HTTP Header Viewer in your browser, no signup

Fetch a URL and displays exactly what HTTP response headers it returns - useful for debugging caching behavior, checking security headers, verifying redirects, or understanding how a server is configured to respond, without needing browser developer tools open.

You should not have to open an IDE to format a snippet from Slack, tidy a JSON blob, or check a hash. Paste it here, copy the result, move on.

HTTP Header Viewer is a good fit when checking Cache-Control and ETag behavior after release.

In plain English

HTTP Header Viewer is built around a few practical wins, not a long feature list:

• Quickly validates real response headers without opening browser devtools.
• Useful for SEO, performance, and security checks from one endpoint call.
• Helps detect CDN/cache misconfiguration early.
• Supports faster verification during deployment troubleshooting.

How to run it

1. Enter the target URL. Paste the full public URL you want to inspect, including protocol (https://).
2. Fetch response headers. Run the request and capture the server-returned header set.
3. Review key header groups. Check caching, security, content, and redirect-related headers in one view.
4. Compare after config changes. Re-run after server updates to confirm headers are deployed correctly.

Real situations

• Checking Cache-Control and ETag behavior after release.
• Verifying security headers like CSP, HSTS, and X-Frame-Options.
• Debugging redirect chains and canonical URL responses.
• Auditing API response headers for cross-team integration readiness.

Small habits that help

• Always test both `www` and non-`www` variants if your site uses redirects.
• Compare headers across staging and production to catch drift.
• Validate that cache headers match asset type and update frequency.
• Use HTTPS endpoints for meaningful security-header audits.

Skip these

• Assuming browser-cached results reflect current server configuration.
• Checking only status code and ignoring missing security headers.
• Auditing one route while other templates return different headers.
• Confusing proxy/CDN headers with your application-level headers.

Does anything leave your device?

HTTP Header Viewer needs the ToolBox API for work a browser cannot do. What you submit is processed, then discarded. It is not kept as a library of your files.

Related tools worth opening next

If this is one step in a longer job, these usually come after it:

• API Tester - Send HTTP requests to any REST API and inspect the response - works with public endpoints and your localhost dev server
• URL Parser - Parse and analyze URL components
• JSON Formatter - Format and validate JSON data

FAQ

What kind of headers will I typically see?

Common ones include Content-Type, Cache-Control, Set-Cookie, security headers like Content-Security-Policy, and server information - exactly what the target server chooses to send back.

Can this check headers on any website?

Publicly accessible URLs generally work; some servers may block requests that don't look like they're coming from a real browser, which could affect what headers you see.

Why would I want to inspect a site's HTTP headers?

Common reasons: debugging why caching isn't working as expected, verifying security headers are configured correctly, or understanding a redirect chain when a URL doesn't go where you expect.

Open the HTTP Header Viewer when you are ready. It is free, and you do not need an account.