Alt Text

TL;DR — Alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. is a short stand-in you add to an image so people who can’t see it — and search engines — know what it’s for. You add it with the alt attribute on the <img> element. It’s one input into accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. (not a guarantee of full compliance by itself), and it helps your images show up in image search. Describe what the image is doing on that page, not just what it shows; don’t stuff in keywords; use an empty alt="" for purely decorative images; and for icon buttons and linked images, describe the action or destination instead.

What alt text is

When you put an image on a web page, the code looks like this:

<img src="dalmatian-puppy.jpg" alt="Dalmatian puppy playing fetch in a park">

That alt="..." part is the alt text — short for alternative text. It’s a written stand-in for the image: a short description of what the picture shows or does. If the image can’t be seen, the alt text is what’s used instead.

You’ll often hear people call it the “alt tag.” That’s the common name, but it’s not quite right — <img> is the tag, and alt is an attribute on it. I’ll use “alt text” and “alt attribute” here, but if you say “alt tag,” everyone will know what you mean.

Good alt text isn’t a fixed description template — it’s chosen for what the image is doing on that particular page, not just what’s visually in it. The same photo could need different alt text (or none at all) in a different spot, depending on what it’s there to communicate and what the surrounding text already says.

Why it matters

Alt text does two important jobs:

• Accessibility. People who are blind or have low vision use screen readers that read pages aloud. When the screen reader hits an image, it reads the alt text. No alt text, and they get nothing useful — or worse, the reader announces the image’s filename. This isn’t just nice-to-have: missing alt text is one of the most common things flagged in website accessibility lawsuits.
• Image SEOImage SEO is optimizing the images on your pages so search engines can discover, crawl, index, and rank them — in Google Images and visual search, and as part of standard web results. It spans file format, filenames, alt text, compression, responsive markup, structured data, and image sitemaps.. Search engines can’t “see” a picture the way you do. The alt text is the main way you tell Google and Bing what an image is about, which helps your images show up in image search.

How to write good alt text

A few simple rules:

• Describe what’s actually in the image, in the context of your page. “Dalmatian puppy playing fetch in a park” is great. “puppy dog pup pups doggies” is keyword stuffing — don’t do that.
• Don’t start with “Image of” or “Photo of.” Search engines and screen readers already know it’s an image. Just describe it.
• Keep it short. A phrase or a sentence. You don’t need a paragraph.
• For decorative images, use an empty alt="". If an image is just a divider line or background flourish that adds nothing, give it alt="" (with nothing between the quotes). That tells screen readers to skip it. Don’t leave the alt attribute off entirely — that’s actually worse. The test: if the image adds no information beyond what the page already says elsewhere, it’s decorative.
• For icon-only buttons and controls, describe the action, not the icon. A search button with a magnifying-glass icon should say alt="Search", not alt="Magnifying glass" — the person needs to know what happens when they activate it.

The thing most people get wrong

Alt text mostly helps image search, not regular web search rankings. A lot of guides imply that adding alt text to your images will boost where your page ranks in normal search results. It really doesn’t work that way — Google’s John Mueller has said this many times. Alt text helps your images get foundA 302 (\"Found\") is a temporary redirect: it forwards users to a new URL while telling search engines the original URL should stay in the index. It's a weak canonicalization signal, not the zero-equity dead end of SEO folklore. in image search, and it adds a little text to the page, but it’s not a magic ranking lever for web search.

Want the precise version — the exact Google quotes, the image-search-vs-web-search distinction, decorative images, linked images, and how to find missing alt text at scale? Switch to the Advanced tab.

TL;DR — Alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. is the value of the alt attribute on an <img> element — required by HTML, an accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. necessity, and the most important piece of image metadata for search. The nuance most guides botch: it primarily affects image search, not web search rankings (Mueller, repeatedly). Google reads it alongside computer vision and page context, so write for context, not bare description. Don’t keyword-stuff, don’t open with “image of,” and use alt="" (not a missing attribute) for decorative images. On a linked image, alt text acts as the anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page.. There’s no Google character limit; 155 chars is a writing guideline. Missing alt is the single most common technical issue on the web — 80.4% of sites have at least one.

What alt text actually is

Alt text is the value of the alt attribute on an HTML <img> element:

<img src="dalmatian-puppy.jpg" alt="Dalmatian puppy playing fetch">

It’s a short text substitute for the image — for screen-reader users, for crawlersA crawler — also called a spider or bot — is an automated program that fetches web pages, extracts their links, and queues new URLs to visit. Search engines use crawlers to discover and download content for their index., and for browsers where the image is disabled or fails to load. One terminology note worth getting right: it’s frequently called the “alt tag,” but that’s a misnomer. The tag is <img>; alt is an attribute on that tag. The label is so entrenched that I won’t fight it, but the precise term is the alt attribute, and the text inside it is alt text.

The alt attribute is required on <img> elements by the HTML specification. Omitting it entirely is a conformance error. An empty value (alt="") is valid and meaningful — it’s the correct way to mark a decorative image (more on that below).

Choosing what to write is not a matter of running through a universal description recipe. The right alt text is a function of the image’s purpose in that specific spot on the page — not a literal inventory of what’s in the frame. The same image can legitimately need different alt text (or an empty one) depending on where it sits and what the surrounding content already conveys; there’s no single “correct” caption independent of context.

Alt text has two separate SEO jobs — and one of them is overstated

This is the distinction most “alt text for SEO” guides blur, and it’s where the real value of this page is. Alt text does two different things for search:

1. It adds text to the page. Google counts alt text as part of the on-page text. Mueller: “The alt text is essentially shown when the images are turned off in most browsers, so that’s something that we would count as part of the on-page text.” That’s real, but small.

2. It signals what an image is about — for image search. This is the primary job. Google’s own documentation calls alt text “the most important attribute” for providing image metadata, and Mueller frames its effect as living in image search: “if someone is searching in Google Images for something that kind of matches the alt text, then we can use that to understand that your image is relevant.”

Here’s the part to internalize: adding alt text does not make a page rank higher in web search simply because it has images. Mueller put it directly: “It’s not the case that we would say a textual webpage has more value because it has images. It’s really just we see the alt text and we apply that to the image, and if someone searches for the image we can use that to better understand the image.”

So if your goal is image-search visibility (and the referral traffic that brings), alt text matters a lot. If you’re hoping alt text alone will lift your blue-link web rankings, you’ve got the wrong tool. This is the same point I make in my JavaScript SEO write-up: for web search, alt text counts as on-page text but its importance is often overstated — its real payoff is image search and accessibility.

It’s not the only signal Google uses

Alt text isn’t read in a vacuum. Google: “Google uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image.” Computer vision can already tell it’s a beach. The alt text’s job is the thing the model can’t infer — the context: why this image is on this page, and what it means here. That’s why Mueller’s 2024 advice lands so well: AI that spits out “photo of a beach” technically describes the pixels but wastes the opportunity, because “the alt-text is unique in that it’s what directly connects the image to the page with context.” The same beach photo might warrant different alt text on a surfing page versus a real-estate listing versus a climate article.

Accessibility — and the legal stakes

Before it’s an SEO asset, alt text is an accessibility requirement. WCAG 2.x Success Criterion 1.1.1 (Non-text Content), Level A requires a text alternative for non-text content. Screen-reader users rely on it; without it, an image is a dead spot in the page, and an omitted alt attribute can make some readers announce the raw filename instead.

That’s one success criterion among dozens. Getting alt text right satisfies 1.1.1 for your images, but it doesn’t by itself establish full WCAG conformance — or ADA compliance — for a page or a site. Those depend on separate criteria too (color contrast, keyboard access, form labels, heading structure, and more). Treat alt text as a necessary piece of accessibility, not the whole of it.

This has teeth. Missing alt attributes are routinely cited in ADA website accessibility lawsuits, which run into the thousands annually in the US. As I note in my JavaScript SEO guide, “missing alt attributes are an accessibility issue, which may turn into a legal issue.” That reframes the fix: it’s a compliance action first, an SEO action second. It’s also why SEO crawlersA crawler — also called a spider or bot — is an automated program that fetches web pages, extracts their links, and queues new URLs to visit. Search engines use crawlers to discover and download content for their index. (Ahrefs Site Audit included) flag missing alt under technical issues.

How to write alt text that works

• Lead with context, not a caption. Describe what the image means for the page, not just what’s visually in it. Mueller, on image search: “you don’t necessarily need to describe exactly what is in the image, but rather kind of like what this image means for your particular page.”
• Don’t start with “Image of” / “Photo of.” Google’s Lizzi Sassman: “We already are aware that it’s an image. You don’t need to say, ‘It’s an image of’ and then the thing.” A descriptive phrase is fine — it doesn’t have to be a full sentence.
• Use keywords naturally, never stuff. Google: “focus on creating useful, information-rich content that uses keywords appropriately and is in context.” And the warning: “Avoid filling alt attributes with keywords… as it results in a negative user experience and may cause your site to be seen as spam.” Gary Illyes put it plainly: the alt text “shouldn’t be what you want to rank for, but what’s in the image.”
• Don’t copy your surrounding paragraph into the alt. Mueller: “I wouldn’t just blindly copy and paste the same text that you already have on a page as an alt text.” The alt attribute is a unique opportunity to add context, not a duplicate.
• There’s no Google character limit. Mueller: “we don’t have any guidelines with regards to how long your alt text can be.” The widely-cited “125 characters” comes from accessibility tools; Google’s Developer Style Guide suggests 155 characters or less as a writing guideline, not a hard cap. Keep it short because long descriptions interrupt the reading flow for screen-reader users — not because Google truncates it.
• Use consistent alt text for repeated images. If the same image appears in multiple places, give it the same alt text.

Decorative images: alt="", not a missing alt

For purely decorative images — spacers, dividers, background flourishes that carry no information — the correct pattern is an empty alt attribute:

<img src="divider.svg" alt="">

alt="" tells assistive technology the image is decorative and should be skipped. This is not the same as leaving the attribute off. Omitting alt entirely is an HTML spec violation, and it can cause some screen readers to read the filename aloud. So: decorative gets alt="" (empty value present), never a missing attribute, and never a description. As I put it in my JavaScript SEO guide — fix alt for the main content images, but for placeholder or decorative images you can leave the alt blank (meaning alt="").

The test for “decorative”: does the image add information the page doesn’t already convey elsewhere — in the surrounding text, a caption, or the page’s structure? If not (a spacer, a repeated icon next to text that already says the same thing, a stock photo used as pure visual filler), it’s decorative and gets alt="". If it does add information nothing else on the page provides, it isn’t decorative, no matter how small or stylistic it looks.

Functional images: describe the action, not the icon

Some images are neither purely decorative nor a simple informative picture — they’re controls: an icon-only search button, a hamburger menu icon, a play button on a video thumbnail. For these, the alt text should describe what activating the control does, not what the icon looks like.

<!-- Weak: describes the icon -->
<button><img src="magnifying-glass.svg" alt="Magnifying glass icon"></button>

<!-- Better: describes the action -->
<button><img src="magnifying-glass.svg" alt="Search"></button>

A screen-reader user who hears “magnifying glass icon” doesn’t know what happens if they activate the control; “Search” tells them immediately. This is the same principle behind linked images below — alt text serves the image’s function on the page — but it applies even when there’s no <a> involved.

Linked images: alt text becomes anchor text

When an image is a link — wrapped in an <a> — its alt text functions as the anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. for that link. Google: “Alt text in images is useful as anchor text if you decide to use an image as a link.” An image-only link with empty alt is the equivalent of an empty anchor text, which is bad for both accessibility (the screen reader can’t describe the destination) and for the link signal. For a linked image, the alt text should describe where the link goes, not just what the picture shows.

Scope this precisely: what Google documents is specifically about using alt text as anchor text for a crawlable link. It’s narrower than the full “accessible name” computation browsers and assistive technology use, which can also pull from aria-label, aria-labelledby, or surrounding link text — alt text is one input into that broader calculation, not the whole of it.

SVGs are different

Inline <svg> elements don’t take an alt attribute — that’s for <img>. To give an inline SVG an accessible name, use a <title> element referenced with aria-labelledby:

<svg role="img" aria-labelledby="logo-title">
  <title id="logo-title">Acme Corp logo</title>
  <!-- paths… -->
</svg>

(An SVG referenced via <img src="logo.svg"> uses a normal alt attribute like any other image — this only applies to inline SVG markup.)

Anti-patterns to avoid

• Keyword stuffing — the spam signal Google explicitly warns about.
• Copying the surrounding paragraph into the alt attribute verbatim.
• “Image of” / “Photo of” openers — redundant.
• Omitting alt on decorative images instead of using alt="".
• AI-generated “photo of X” descriptions that ignore page context.
• Putting your company name in blank alt attributes. Mueller was blunt about this one: “It makes no sense, it seems like a waste of time to me: once wasted time to implement, and again wasted time to clean up later on.”
• Confusing alt with the title attribute. The title attribute shows as a hover tooltip; it’s not alt text and carries little SEO or accessibility weight.

Finding and fixing missing alt text

Missing alt attributes aren’t an edge case — they’re the default failure state of the web. In our site audit study of over a million domains, 80.4% of sites had missing alt attributes on at least one page, making it the single most prevalent technical SEOTechnical SEO is the practice of making a site easy for search engines to crawl, render, index, and (now) be eligible for AI answers. It's the foundation that lets your content and links rank — not a ranking trick of its own. issue we foundA 302 (\"Found\") is a temporary redirect: it forwards users to a new URL while telling search engines the original URL should stay in the index. It's a weak canonicalization signal, not the zero-equity dead end of SEO folklore..

To find them:

• Ahrefs Site Audit → Images report flags images missing alt attributes across your site. (Ahrefs Webmaster ToolsThe free, first-party consoles search engines give site owners — Google Search Console and Bing Webmaster Tools — to see how their pages are crawled, indexed, and ranked, and to fix problems. The legacy name is 'webmaster tools.' gives you this free for sites you verify.)
• Manual spot-checks — inspect element on key content images, or use a browser accessibility extension.

Priority order when you fix them:

1. Main content images first — the ones that carry meaning and can earn image search traffic.
2. Linked images — empty alt here is doubly costly (anchor text + accessibility).
3. Decorative images last — and the fix is alt="", not a description.

TIP Turn missing alt text into a review queue

The useful output is the affected image paths; each still needs a human decision about meaning, decoration, and link purpose.

Scan a page for missing alt attributes and related image issues with my free Image SEO Checker Free

1. Review each reported image in its page context.
2. Write concise contextual alt for meaningful images and destination-focused alt for image links.
3. Use alt="" for genuinely decorative images instead of inventing a description.

Tap to enlarge

A note on expectations: SearchPilot’s split tests on adding alt text have been inconclusive / not statistically significant for web rankings — consistent with the point above that alt text’s payoff is in image search and accessibility, not a web-ranking boost. And Mueller’s reassurance for sites starting from zero coverage: “if you’re just adding alt text for the first time, then sometimes, even any alt text is better than nothing.”

To be direct about it: nothing in this piece backs a guarantee that fixing alt text moves rankings, traffic, or AI-search citations by any set amount — no reviewed official source makes that promise, and the split-test evidence above is inconclusive. What alt text reliably does is close an accessibility gap and give Google’s Image Search algorithm metadata it explicitly says it uses.

For the bigger picture — filenames, image sitemapsAn image sitemap is a sitemap (or an extension added to an existing sitemap) that lists the images on your pages using Google's image namespace, helping Google discover images it might otherwise miss., lazy-loading, formats, and responsive images — see the broader image SEOImage SEO is optimizing the images on your pages so search engines can discover, crawl, index, and rank them — in Google Images and visual search, and as part of standard web results. It spans file format, filenames, alt text, compression, responsive markup, structured data, and image sitemaps. hub this article sits under.

AI summary

A condensed take on the Advanced version:

• What it is: alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. is the value of the alt attribute on an <img> element — a short text substitute chosen for the image’s purpose and context, not a literal inventory of pixels. Required by HTML. Commonly miscalled the “alt tag” (<img> is the tag; alt is the attribute).
• Two SEO jobs, one overstated: (1) it adds on-page text — real but minor; (2) it signals what an image is about for image search — the primary value. Adding alt text does not lift web rankings just because a page has images (Mueller, repeatedly), and no reviewed official source promises a ranking, traffic, or AI-citation outcome from adding it.
• Not the only signal: Google reads alt text with computer vision and page context. So write for context — why the image is on this page — not a bare “photo of a beach” caption.
• AccessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. + legal: WCAG 1.1.1 (Level A) requires a text alternative; missing alt is a frequent ADA lawsuit item. But 1.1.1 is one criterion among dozens — alt text alone doesn’t establish full WCAG conformance or ADA compliance for a page or site. Compliance first, SEO second.
• Writing rules: lead with context; don’t open with “image of”; use keywords naturally (no stuffing, no fixed formula); don’t copy the surrounding paragraph; no Google character limit (155 chars is a style-guide writing target, not a cap).
• Decorative images: use alt="" (empty value present) — not a missing attribute, and not a description. Test: does it add information the page doesn’t already convey elsewhere? If not, it’s decorative.
• Functional images: icon-only buttons and controls (search icon, hamburger menu) get alt text describing the action, not the icon’s appearance.
• Linked images: alt text acts as anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. for a crawlable link — narrower than the full “accessible name” computation assistive tech uses.
• SVG: inline SVGs use <title> + aria-labelledby, not alt.
• Anti-patterns: keyword stuffing, company-name-in-blank-alt (Mueller: “a waste of time”), confusing alt with the title tooltip attribute.
• Scale of the problem: 80.4% of sites have at least one missing alt attribute — the most common technical issue on the web. Audit with Ahrefs Site Audit’s Images report; fix content images first, decorative (alt="") last.

Official documentation

Primary-source documentation from the search engines.

Google

• Google Images best practices — the core reference: alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. as “the most important attribute,” the keyword-stuffing warning, image-as-link anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page., and good/bad examples.
• SEO Starter Guide — descriptive alt text — alt text as the text that “explains the relationship between the image and your content.”
• Developer Documentation Style Guide — alt text — the 155-character writing guideline, alt="" for decorative images, no “Image of”/“Photo of,” and include punctuation.
• Write helpful alt text (Technical Writing) — Google’s accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all.-focused how-to: keep it short, explain in context, consistent alt for repeated images.
• web.dev — Text alternatives for images — descriptive alt for important images, empty alt="" for decorative ones.

Bing / Microsoft

• Architecting content for SEO (SEM 101) — older Bing post framing images as “dead zones to a botA crawler — also called a spider or bot — is an automated program that fetches web pages, extracts their links, and queues new URLs to visit. Search engines use crawlers to discover and download content for their index.” and alt attributes as how you describe them (use relevant keywords, don’t force).
• Being a Part of the Bing Image Search Ecosystem — filenames and alt text helping a page surface in the image carousel even when it doesn’t rank on page one of web search.

Quotes from the source

On-the-record statements from Google. Where a page exposes the text, the link is a deep link that jumps to the quoted passage.

Google docs — what alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. is for

• “The most important attribute when it comes to providing more metadata for an image is the alt text… which also improves accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. for people who can’t see images on web pages.” Jump to quote
• “Google uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image.” Jump to quote
• “Avoid filling alt attributes with keywords (also known as keyword stuffing) as it results in a negative user experience and may cause your site to be seen as spam.” Jump to quote
• “Alt text in images is useful as anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. if you decide to use an image as a link.” Jump to quote

John Mueller, Google — alt text is for image search

• “When it comes to the alt text, we primarily use that to better understand the image. So if someone is searching in Google Images for something that kind of matches the alt text, then we can use that to understand that your image is relevant for that alt text on that specific page.” — Office Hours, March 18 2022. Listen · SEJ coverage
• “It’s not the case that we would say a textual webpage has more value because it has images. It’s really just we see the alt text and we apply that to the image, and if someone searches for the image we can use that to better understand the image.” — Office Hours, March 18 2022.
• “I think the important part here is we don’t have any guidelines with regards to how long your alt text can be.” — Office Hours, March 18 2022.
• “The alt-text is unique in that it’s what directly connects the image to the page with context… if you use AI to create alt texts based on the image file, and get ‘photo of a beach’ as the alt text for that image, you’re not getting the most out of the alt text, both for users & search engines.” — Reddit r/SEO, September 2024. Thread · SEJ coverage
• On putting a company name into blank alt attributes: “It makes no sense, it seems like a waste of time to me: once wasted time to implement, and again wasted time to clean up later on.” — Twitter, June 2 2022. Coverage

Lizzi Sassman, Google — don’t say “image of”

• “We already are aware that it’s an image. You don’t need to say, ‘It’s an image of’ and then the thing.” — Search Off the Record, “Let’s talk image SEOImage SEO is optimizing the images on your pages so search engines can discover, crawl, index, and rank them — in Google Images and visual search, and as part of standard web results. It spans file format, filenames, alt text, compression, responsive markup, structured data, and image sitemaps.,” October 2022. Transcript

Gary Illyes, Google — describe the image, don’t keyword-target

• “Make sure to add alt attribute. This text shouldn’t be what you want to rank for, but what’s in the image.” — Pubcon keynote, October 17 2018. Coverage

Alt text audit checklist

A pass to catch the alt-text problems that actually matter — accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. first, image SEOImage SEO is optimizing the images on your pages so search engines can discover, crawl, index, and rank them — in Google Images and visual search, and as part of standard web results. It spans file format, filenames, alt text, compression, responsive markup, structured data, and image sitemaps. second:

• Missing alt attributes on content images — the #1 issue (80.4% of sites have at least one). Fix these first.
• Decorative images use alt="" (empty value present), not a missing attribute and not a description.
• No omitted alt anywhere — an absent attribute is an HTML spec violation and can make screen readers read the filename.
• Linked images have meaningful alt describing the destination (alt = anchor text on a linked image; empty alt = empty anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page.).
• Functional images (icon-only buttons/controls) describe the action — alt="Search", not alt="Magnifying glass icon".
• No keyword stuffing — no strings of synonyms or target keywords crammed in.
• No “Image of” / “Photo of” openers — lead straight into the description.
• Alt isn’t a copy of the surrounding paragraph — it should add unique context for that image.
• Alt describes context, not just visuals — what the image means on this page, not a generic “photo of a beach.”
• No company name dumped into blank alt attributes (Mueller: “a waste of time”).
• alt not confused with title — the title attribute is a hover tooltip, not alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search..
• Repeated images use consistent alt text.
• Inline SVGs use <title> + aria-labelledby rather than an alt attribute.
• Mobile = desktop alt text — the mobile version carries the same alt text as desktop (mobile-first indexingGoogle's practice of using the mobile version of a page's content — crawled by Googlebot smartphone — for indexing and ranking. It is not a separate index and not a ranking boost.).
• Audit at scale with Ahrefs Site Audit’s Images report (or Ahrefs Webmaster Tools, free for verified sites).

Resources worth your time

My related writing

• JavaScript SEO Issues & Best Practices — where I cover blank alt attributes left behind by JS frameworks, the accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all.-and-legal angle, and why alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search.’s web-search importance is often overstated.
• Ahrefs Site Audit Study — the study of 1M+ domains where missing alt attributes turned out to be the most common technical SEOTechnical SEO is the practice of making a site easy for search engines to crawl, render, index, and (now) be eligible for AI answers. It's the foundation that lets your content and links rank — not a ranking trick of its own. issue (80.4% of sites).
• The Beginner’s Guide to Technical SEO — where image and alt-text handling fit into the bigger technical picture.

Official

• Google’s Google Images best practices — the canonical reference for alt text and image metadata.
• Google’s Developer Documentation Style Guide — alt text — concrete writing rules (155 chars, alt="", no “Image of”).
• WCAG 2.1 — Non-text Content (1.1.1) — the accessibility success criterion behind alt text.

From others

• SearchPilot’s split tests on alt text — adding alt text (inconclusive) and descriptive alt text on listing images (estimated lift, not statistically significant) — useful real-world tempering of “alt text boosts web rankings.”
• Search Engine Journal — Mueller on alt text for SEO (March 2022) — write-up of the Office Hours where Mueller draws the image-search vs. web-search line clearly.
• Search Engine Journal — Mueller’s 2024 “photo of a beach” context advice — covers his Reddit comment on why AI-generated descriptions miss the point of alt text.
• SE Roundtable — Google on company names in blank alt text (June 2022) — Barry Schwartz’s coverage of Mueller calling the practice “a waste of time.”
• Search Off the Record — “Let’s talk image SEO” (Oct 2022, transcript) — Mueller and Lizzi Sassman on context-first alt text, the “image of” opener mistake, and when any alt text beats none.
• W3C — WCAG 2.1 Success Criterion 1.1.1 (Non-text Content) — the Level A accessibility requirement underpinning why missing alt is a compliance issue, not just an SEO one.
• web.dev — Text alternatives for images — Google’s developer guidance distinguishing descriptive alt for meaningful images from empty alt="" for decorative ones.

Alt text mistakes worth naming individually

Keyword stuffing, “image of” openers, and missing alt on decorative images are the three mistakes I see most, but they’re not the only ones. Each entry here is a mistake with a reason it’s wrong and what to do instead.

Keyword stuffing the alt attribute

Why it’s wrong: Google explicitly warns against this — “Avoid filling alt attributes with keywords… as it results in a negative user experience and may cause your site to be seen as spam.” A screen reader reads the alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. aloud, so alt="puppy dog pup pups doggies" isn’t just spammy to a crawlerA crawler — also called a spider or bot — is an automated program that fetches web pages, extracts their links, and queues new URLs to visit. Search engines use crawlers to discover and download content for their index., it’s unusable to a real listener.

Do instead: Describe the image in plain language, in context. alt="Dalmatian puppy playing fetch in a park" says the same information without the keyword pile.

Opening with “Image of” or “Photo of”

Why it’s wrong: Google’s Lizzi Sassman was direct about this: “We already are aware that it’s an image. You don’t need to say, ‘It’s an image of’ and then the thing.” Every character spent on the redundant opener is a character not spent on useful context.

Do instead: Start the description immediately — alt="Dalmatian puppy playing fetch in a park", not alt="Image of a dalmatian puppy playing fetch in a park".

Omitting the alt attribute on decorative images

Why it’s wrong: Leaving alt off entirely (rather than setting it to an empty string) is an HTML spec violation, and it can make some screen readers announce the raw filename instead of staying silent.

Do instead: Use alt="" — an empty value, attribute present — for genuinely decorative images like dividers and background flourishes. That tells assistive technology to skip the image cleanly.

Using AI-generated “photo of X” descriptions that ignore page context

Why it’s wrong: Mueller called this out directly: AI tools that spit out “photo of a beach” technically describe the pixels but miss the point, because “the alt-text is unique in that it’s what directly connects the image to the page with context.” A bare visual caption throws away the one thing alt text can do that computer vision can’t.

Do instead: Write (or edit an AI draft) to explain what the image means on this page — the same beach photo needs different alt text on a surfing page than on a real-estate listing.

Putting your company name into blank alt attributes

Why it’s wrong: Mueller called this specific pattern a waste of effort: “It makes no sense, it seems like a waste of time to me: once wasted time to implement, and again wasted time to clean up later on.” It adds no information to either users or search engines and just becomes cleanup debt later.

Do instead: Either write real, image-specific alt text or use alt="" for genuinely decorative images. Don’t default to a boilerplate brand name.

Describing an icon-only control’s appearance instead of its action

Why it’s wrong: alt="Magnifying glass icon" on a search button tells a screen-reader user what the icon looks like, not what pressing it does. For a functional control, appearance isn’t the useful information — the action is.

Do instead: Name the action or result: alt="Search", alt="Close menu", alt="Play video". This is the same principle as a linked image’s alt text acting as anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. — the alt text should serve the control’s function.

Confusing the alt attribute with the title attribute

Why it’s wrong: The title attribute renders as a hover tooltip in most browsers. It isn’t read by screen readers the way alt text is, and it carries little SEO weight — treating it as a substitute for alt text leaves both accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. and image search unaddressed.

Do instead: Set alt for the text substitute every image needs; use title only for genuine supplementary tooltip text, if at all.

Before/after alt text examples

Four concrete before/after pairs pulled straight from the rules above.

Keyword-stuffed vs. descriptive

<!-- Before: keyword stuffing -->
<img src="dalmatian-puppy.jpg" alt="puppy dog pup pups doggies dalmatian puppies for sale">

<!-- After: plain description -->
<img src="dalmatian-puppy.jpg" alt="Dalmatian puppy playing fetch in a park">

The “after” version describes what’s actually in the image once, in plain language, instead of cramming in every synonym and buyer-intent phrase Google warned against.

Generic caption vs. context-aware alt

The same beach photo needs different alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. depending on the page it sits on — this is the distinction Mueller drew when he criticized AI tools that output “photo of a beach” regardless of context.

<!-- Generic, low-value -->
<img src="beach.jpg" alt="Photo of a beach">

<!-- On a surfing page -->
<img src="beach.jpg" alt="Surfer paddling out past the break at sunrise">

<!-- On a real-estate listing -->
<img src="beach.jpg" alt="Private beach access behind the oceanfront property">

Same pixels, three different jobs — the alt text should match the page’s purpose, not just narrate the image.

Decorative image: empty alt vs. missing alt

<!-- Wrong: attribute omitted entirely -->
<img src="divider.svg">

<!-- Right: empty value, attribute present -->
<img src="divider.svg" alt="">

Both look similar at a glance, but they behave differently: the omitted attribute is an HTML spec violation that can make some screen readers announce the filename; the empty alt="" correctly tells assistive technology to skip the image.

Functional image: action vs. appearance

<!-- Weak: describes the icon -->
<button><img src="magnifying-glass.svg" alt="Magnifying glass icon"></button>

<!-- Better: describes what the control does -->
<button><img src="magnifying-glass.svg" alt="Search"></button>

The button isn’t a link and isn’t decorative — it’s a control. Naming the icon tells a screen-reader user nothing about what happens if they press it; naming the action does.

Linked image: alt as anchor text

<!-- Weak: doesn't describe the destination -->
<a href="/pricing/"><img src="cta-button.png" alt="Button"></a>

<!-- Better: alt describes where the link goes -->
<a href="/pricing/"><img src="cta-button.png" alt="View pricing plans"></a>

Because the image is wrapped in a link, its alt text functions as the anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. — “Button” tells a screen-reader user nothing about the destination, while “View pricing plans” does.

What alt text should this image get?

Three quick branches for the decisions that come up on almost every image: is it decorative, is it a control rather than a picture, and is it wrapped in a link.

Common issues with alt text

Four symptom-cause-fix entries for the alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. problems that actually show up in audits and accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. reviews.

A screen reader announces the raw filename instead of a description

Symptom: A screen reader reads something like “dalmatian-puppy-jpg” or “IMG_4021” aloud instead of a description.

Likely cause(s): The alt attribute was omitted from the <img> element entirely, rather than set to an empty string. This is an HTML spec violation, and it’s the default failure state — missing alt attributes show up on 80.4% of sites according to Ahrefs’ site audit study of over a million domains.

Fix + check: Add a descriptive alt for content images, or alt="" for genuinely decorative ones. Confirm with a browser accessibility extension or by inspecting the element — the attribute should be present either way.

Missing alt attributes flagged across the whole site

Symptom: An audit tool comes back with hundreds or thousands of images flagged for missing alt attributes.

Likely cause(s): No systematic process for adding alt text as images are uploaded, often compounded by a CMSA content management system (CMS) is software that lets users create, manage, and publish digital content — like blog posts and pages — without writing raw code. WordPress, Drupal, and Joomla are the most common open-source CMS platforms. or theme that doesn’t require it at upload time.

Fix + check: Prioritize in order — main content images first (they carry meaning and can earn image search traffic), linked images second (empty alt there costs you anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. too), decorative images last (and the fix there is alt="", not a description). Re-run the Image SEO Checker or your site audit tool after each pass to confirm the count is dropping.

Images aren’t showing up in Google Images despite having alt text

Symptom: Content images have alt text, but they still don’t appear for relevant Google Images searches.

Likely cause(s): The alt text is a generic visual caption (“photo of a beach”) rather than context-specific description of what the image means on that page — Mueller has said this kind of generic AI-generated alt text under-delivers. It’s also worth remembering alt text is only one signal: Google combines it with computer vision and page context, so a thin or unrelated surrounding page can hold an image back even with good alt text.

Fix + check: Rewrite the alt text to reflect the page’s actual subject and purpose, not just the pixels. Recheck performance in Search ConsoleA free Google service that reports how a site performs in Google Search and surfaces problems with how Google crawls, indexes, and serves it. It's first-party data straight from Google — but you don't need it to appear in results. → Performance → Search type: Image after Google has had time to recrawlCrawl frequency is how often a search engine comes back to re-fetch a page it already knows about. Popular pages that change often get refreshed many times a day; stable pages can go weeks or months between crawls — and you influence it indirectly, not by setting a dial. and reprocess.

An icon-only button doesn’t tell screen-reader users what it does

Symptom: A screen reader announces something like “magnifying glass icon” or “button image” before an icon-only control, with no indication of what pressing it does.

Likely cause(s): The alt text describes the icon’s appearance instead of the control’s action — a common mix-up because the image looks like a normal picture, not a link or a purely decorative element.

Fix + check: Rewrite the alt text to name the action or result (alt="Search", alt="Close menu", alt="Play video"), not the icon. Confirm by tabbing to the control with a keyboard and listening to what a screen reader announces.

A linked image’s destination isn’t clear to screen-reader users

Symptom: A user navigating by link (or by image) via screen reader hears nothing useful before activating an image-only link.

Likely cause(s): The linked image has empty or missing alt text — the equivalent of an empty anchor textAnchor text is the visible, clickable text of a hyperlink. It tells readers what they'll find on the other end and gives search engines context about the linked page. on a text link.

Fix + check: Write alt text that describes where the link goes, not just what the image shows (see the Examples tab for a before/after). Confirm by tabbing to the link with a keyboard and checking what a screen reader announces, or by inspecting the element.

The standing KPIs for image alt text

Two things worth tracking on an ongoing basis, not just after a one-time cleanup: how much of the site has alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. at all, and whether that alt text is actually earning image search visibility.

Alt text coverage across the site

• Metric — The share of <img> elements site-wide that have a non-empty, non-decorative alt attribute (content images only — decorative images should correctly show alt="", which isn’t a gap).
• What it tells you — Whether alt text is a one-time fix or an ongoing habit. Given that 80.4% of sites in Ahrefs’ site audit study have at least one missing alt attribute, coverage tends to erode again as new content gets published unless it’s checked regularly.
• How to pull it — The Image SEO Checker on a page, Ahrefs Site Audit’s Images report across a full crawl, or a browser accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. extension for spot-checks.
• Benchmark / realistic range — There’s no universal target percentage — a site with a lot of decorative background imagery will legitimately show more alt="" than a photo-heavy blog. Baseline your own current coverage the first time you check, then watch that it isn’t sliding backward as new pages ship.
• Cadence — Quarterly as a standing check, and immediately after any bulk content migration or CMSA content management system (CMS) is software that lets users create, manage, and publish digital content — like blog posts and pages — without writing raw code. WordPress, Drupal, and Joomla are the most common open-source CMS platforms./theme change that touches how images get uploaded.

Image search performance (Google Images impressions/clicks)

• Metric — Impressions, clicks, and CTR for your site filtered to Image search results.
• What it tells you — Whether the alt text you’re writing is actually translating into image search visibility and traffic — the primary job Mueller has repeatedly said alt text does, as opposed to a web-ranking boost.
• How to pull it — Search ConsoleA free Google service that reports how a site performs in Google Search and surfaces problems with how Google crawls, indexes, and serves it. It's first-party data straight from Google — but you don't need it to appear in results. → Performance → Search type: Image.
• Benchmark / realistic range — Depends entirely on how image-heavy the site and its topic are — there’s no defensible universal number. Establish your own baseline the first time you pull this report, then track the trend after alt text or image content changes rather than comparing to any external benchmark.
• Cadence — Monthly as a standing check; watch it more closely for a few weeks after any bulk alt-text rewrite to see whether it moves.

Tools for auditing and fixing alt text

• Image SEO Checker — audits raw HTML image signals directly, including alt attributes, lazy-loading hints, and image formats. It’s the fastest way to spot-check a single page’s alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. coverage before or after a fix.
• On-Page SEO Checker — gives a prioritized on-page memo plus advanced raw-HTML checks covering images alongside headings, links, and other on-page elements, useful when alt text is one of several things you’re auditing on a page at once.
• Ahrefs Site Audit — Images report — flags images missing alt attributes across a full crawl of your site (Ahrefs Webmaster ToolsThe free, first-party consoles search engines give site owners — Google Search Console and Bing Webmaster Tools — to see how their pages are crawled, indexed, and ranked, and to fix problems. The legacy name is 'webmaster tools.' gives you this free for verified sites), which is how the 80.4% missing-alt figure in Ahrefs’ site audit study was measured.
• Search ConsoleA free Google service that reports how a site performs in Google Search and surfaces problems with how Google crawls, indexes, and serves it. It's first-party data straight from Google — but you don't need it to appear in results. — Performance, Search type: Image — the source of truth for whether your alt text is actually earning image search impressions and clicks.
• Browser accessibilityWeb accessibility means designing sites so people with disabilities can use them, per the W3C's WCAG guidelines. It overlaps with SEO in specific, checkable ways — alt text, heading structure, descriptive link text, captions, and page speed all serve both audiences — but Google has said accessibility itself is not a ranking factor, and most WCAG success criteria (keyboard focus order, ARIA live regions, form labels) have no SEO effect at all. extensions / inspect element — for manual spot-checks on key content images, and for confirming what a screen reader will actually announce.

Test yourself: alt text

Five quick questions on what alt textAlt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search. actually does and how to write it. Pick an answer for each, then check.

Alt Text

Alt text is the value of the `alt` attribute on an HTML `<img>` element — a short text substitute chosen for the image's purpose and context, not a literal description of what it shows. It makes images accessible to screen-reader users and helps search engines understand images, mainly for image search.

Related: Image SEO, Accessibility (Web Accessibility)

Alt Text

Alt text (short for alternative text) is the value of the alt attribute on an HTML <img> element. It’s a short text substitute chosen for what the image is doing on that specific page — its purpose and context — rather than a fixed inventory of what’s visually in the frame. It’s addressed to anyone, or anything, that can’t see the picture itself: blind and low-vision users on screen readers, search engine crawlersA crawler — also called a spider or bot — is an automated program that fetches web pages, extracts their links, and queues new URLs to visit. Search engines use crawlers to discover and download content for their index., and browsers renderingTurning HTML, CSS, and JavaScript into the final visual page and DOM. with images turned off or failing to load.

<!-- Descriptive -->
<img src="dalmatian-puppy.jpg" alt="Dalmatian puppy playing fetch in a park">

<!-- Decorative — intentionally empty -->
<img src="divider.svg" alt="">

The attribute is commonly (and technically incorrectly) called the “alt tag.” The element is <img>; alt is an attribute on it, not a tag of its own. The alt attribute is required on <img> elements by the HTML specification, even when its value is an empty string — and an empty alt="" is the correct, intentional signal for a purely decorative image, telling assistive technology to skip it.

For SEO, alt text does two distinct jobs. It adds text to the page (counted as on-page text) and, more importantly, it’s a primary signal for image search rankings — Google reads it alongside computer vision and page context to understand what an image is about. Its effect on regular web search rankings is limited; a page doesn’t rank higher in web search simply because its images carry alt text.

Related: Image SEO, Accessibility (Web Accessibility)

Changelog