Langues

HTTP Header Checker

Free, no signup. See the headers browsers and crawlers receive: every redirect hop, separate security and SEO grades, edge fingerprints, compression, and an honest HTTP/3 signal.

Built by Patrick Stox

Request user-agent

A matching user-agent does not make this request originate from that crawler’s verified IP range.

This makes two user-triggered requests for one URL from Cloudflare infrastructure. It compares user-agent responses, not verified crawler behavior or crawler IP access.

Compare staging or another URL

The report compares the final response headers from two independent checks.

Checks run from our server; we fetch the URL you enter and don't keep the results. Complete response header maps are returned to your browser. Repeating the same URL and user-agent within about ten minutes may reuse a short-lived edge cache. Anonymous run-level outcome counters may be used for aggregate research; URLs, domains, IPs, and identifiers are never included, and no statistic is released below 100 runs.

Feedback
Report a bug

Found something broken in Http Header Checker? Let us know what happened — this goes straight to a private triage queue, not a public list.

What will be sent 
 No tool inputs, uploads, pasted source, complete results, query parameters, or URL fragments are attached automatically. You can edit or remove the selected passage above. Browser and anti-abuse metadata is processed for spam prevention. 
  
 
  
 
 
  
 
 
   
 
 Compare common headers across up to five URLs    
Frequency is calculated in this browser from the live final responses in this run. It is not a global popularity dataset.
   
 
 
Sample report
Illustrative example — exact grading for the fixed header map below
HTTP/2 200
strict-transport-security: max-age=31536000
cache-control: public, max-age=3600
etag: "abc123"
Security headers
F40/100
HSTS passes. Missing CSP fails; missing framing protection, Referrer-Policy, nosniff, Permissions-Policy, and COOP are warnings. Missing COEP is informational.
SEO headers
A+100/100
Cache-Control and ETag pass. Missing X-Robots-Tag, Link canonical, and Vary are informational in this HTTP-only grade.
The displayed HTTP/2 line is illustrative input only: the live Worker cannot expose the negotiated HTTP version.
 
 
 
How to use it
 
  1. Enter a public URL and choose the browser, search-crawler, or AI-crawler user-agent you want to send.
  2. Optionally add a staging or comparison URL; only final-response headers are diffed.
  3. Choose Check headers, start with the two grades, then inspect the exact finding and header evidence.
  4. Review every redirect response and use the raw curl-style view when you need to copy the complete observed map.
 
 
 
       
     
     
 
What the results mean
  • Security grade deducts 20 points per failure and 8 per warning across the implemented header rules.
  • SEO grade evaluates X-Robots-Tag, Link canonical and hreflang, Vary, cache directives, and ETag.
  • Pass confirms one rule; info is context without a score penalty.
  • Delivery fingerprint is evidence about a public edge, not proof of the origin host.
  • Comparison lists changed final-response header values, not HTML or behavior differences.
 
How it works
A bounded server-side checker sends the selected user-agent, records each redirect response without hiding intermediate headers, and returns normalized header maps and timings. Browser-side functions grade the final response, parse Link headers, inspect compression and protocol advertisements, identify a small set of edge fingerprints, produce a curl-style view, and diff an optional second final response. The small batch mode counts fields only across the final responses fetched in that run and labels names from a local status-preserving snapshot of the IANA HTTP Field Name Registry.
 
Features
  • Complete headers for every observed redirect hop.
  • Separate deterministic security and HTTP-level SEO grades.
  • Browser, Googlebot, and supported crawler user-agent choices.
  • Compression, edge fingerprint, and honest HTTP/3 advertisement facts.
  • Optional final-response environment diff and raw header export view.
  • Session-local common-header frequency for up to five URLs.
 
Limitations
 
The report cannot expose negotiated HTTP version, TLS certificate details, private origin infrastructure, or headers added only inside a user's network. The Fetch Headers API may combine repeated field lines: parsed combined values are assessed, but the original field-line order and boundaries cannot be reconstructed. User-agent strings originate from a Cloudflare datacenter, not verified crawler IP ranges. It does not inspect HTML metadata, application security, or whether a 200 body is correct.
 
Frequently asked questions
 
Does the tool preserve repeated header field lines?
Not exactly. The Worker Fetch Headers API exposes a normalized, potentially combined value. The checker parses and assesses that combined value, but it cannot reconstruct the original order or boundaries of repeated field lines.
Does this show the HTTP version?
Workers do not expose the negotiated HTTP version. The tool only reports when Alt-Svc advertises HTTP/3; that is not proof this request used HTTP/3.
Why do browser and Googlebot results differ?
Sites can vary headers by user-agent. This sends the selected user-agent string from a Cloudflare datacenter, not from a verified crawler IP range.
Are URLs saved?
No. The URL is fetched to build this report and a short-lived edge cache may reuse the same URL and user-agent response for about ten minutes.
Is a high security-header grade proof that a site is secure?
No. The grade covers a defined set of public response headers. It does not test application vulnerabilities, authentication, server configuration, dependency risk, or whether a policy works correctly for the application.
Does the SEO grade inspect HTML canonical and robots tags?
No. It evaluates HTTP-level signals such as X-Robots-Tag and Link headers. Page-level canonical and robots elements require an HTML-aware checker.
 
Next stepHosting Checker — look up the exact spec and expected values.

People also explore
ToolDNS CheckerToolWebsite Down CheckerToolDomain ReportArticleMixed ContentArticleCaching for SEOArticleWebsite Hosting Migration SEO
 
 
 
Feature requests for Http Header Checker
 

Upvote what you want most. New ideas can be submitted from the floating Feedback menu;
      requests appear here once approved, and the most-wanted rise to the top.

   
Loading…
  
  ➕ Request a feature   
New requests are reviewed before they appear here.
 
     
  
  
 
 
 
 
    
 
 
   
À propos de l’outil
Inspectez les en-têtes HTTP complets de chaque saut de redirection, avec des notes de sécurité et de SEO séparées, les empreintes CDN, la compression et un signal HTTP/3 honnête. Comparez une URL de préproduction à la production et exportez la vue brute.
Fonctionnalités
  • Analyse des en-têtes finaux et intermédiaires avec notes de sécurité et SEO déterministes.
  • Choix de user-agent navigateur, Googlebot et robots pris en charge, plus comparaison d’environnement facultative.
  • Diagnostic de cache, fréquence des en-têtes pour cinq URL et vue brute au format curl.
  • Détection des en-têtes HSTS, CSP, robots, canonical, hreflang, Vary, cache et ETag.
Fonctionnement
Le vérificateur envoie le user-agent choisi, conserve chaque réponse de redirection et renvoie des cartes d’en-têtes normalisées. Les fonctions du navigateur notent la réponse finale, analysent Link, compression, protocoles et empreintes de périphérie, puis comparent une seconde réponse facultative.
Limites
  • La Fetch Headers API peut fusionner des lignes répétées ; les valeurs combinées sont évaluées, mais l’ordre original ne peut pas être reconstruit.
  • Le Worker n’expose ni la version HTTP négociée, ni les détails TLS, ni l’infrastructure privée d’origine, ni les métadonnées HTML de la page.
Questions fréquentes
Une note élevée d’en-têtes de sécurité prouve-t-elle qu’un site est sécurisé ?
Non. La note couvre un ensemble défini d’en-têtes publics et ne teste ni vulnérabilités applicatives, ni authentification, ni configuration serveur, ni risque de dépendance.
Le tool conserve-t-il les lignes répétées d’un champ ?
La valeur normalisée éventuellement combinée est évaluée, mais l’API ne permet pas de reconstruire l’ordre ou les limites des lignes originales.
Les URL sont-elles enregistrées ?
Non. L’URL est récupérée pour produire le rapport ; une cache de périphérie de courte durée peut réutiliser la réponse pendant environ dix minutes.
La note SEO inspecte-t-elle le canonical et les robots HTML ?
Non. Elle évalue les signaux HTTP comme X-Robots-Tag et Link. Les éléments canonical et robots dans le HTML nécessitent un vérificateur conscient du HTML.
Le rapport montre-t-il la version HTTP ?
Non. Le Worker signale seulement lorsqu’Alt-Svc annonce HTTP/3 ; cela ne prouve pas que cette requête a utilisé HTTP/3.