HTTP Headers Reference

Browse 40+ standard headers by category (request, response, security, CORS, caching) with descriptions and usage examples.

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About http headers reference

HTTP Headers Reference loads once and then runs on its own. Close the tab and there is nothing left behind, on the machine or anywhere else.

Once the page has loaded it needs nothing further from the network. Work on a plane, on a train, or behind a firewall that blocks everything.

You will find it under Network, alongside 17 other tools for the same sort of job.

Search by name or description.

How to use it

01
Start it
Every control is on the tool itself. Keyboard shortcuts, where there are any, are listed beside it.
02
Watch it run
It updates in the page as you go. Nothing is sent anywhere, so it keeps working with the network off.
03
Close when done
Nothing is stored between visits. Reloading gives you a clean start rather than picking up where you left off.

Examples

Browse security-related HTTP headers
List all security headers like HSTS, CSP, X-Frame-Options with descriptions
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category: security
search:
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Strict-Transport-Security [security]
  Force HTTPS connections
  Example: Strict-Transport-Security: max-age=31536000; includeSubDomains

X-Content-Type-Options [security]
  Prevents MIME type sniffing
  Example: X-Content-Type-Options: nosniff

X-Frame-Options [security]
  Controls iframe embedding
  Example: X-Frame-Options: DENY

X-XSS-Protection [security]
  Enables cross-site scripting filter
  Example: X-XSS-Protection: 1; mode=block

Content-Security-Policy [security]
  Controls resources the user agent is allowed to load
  Example: Content-Security-Policy: default-src 'self'

Referrer-Policy [security]
  Controls how much referrer info is sent
  Example: Referrer-Policy: strict-origi…

Questions

Does HTTP Headers Reference work offline?+

Yes. It is JavaScript running in this tab, so once the page has loaded it needs nothing further from the network. Put the machine in flight mode and it carries on. Nothing you do here is sent anywhere, because there is nowhere for it to go.

Does it remember anything between visits?+

No. Reload the page and it starts from nothing. There is no account, no saved state and no cookie holding your last session. That is a deliberate trade: it cannot lose your data because it never keeps any.

Is it accurate?+

Timing comes from performance.now(), the high resolution clock the browser provides, rather than from setInterval, which drifts by a few milliseconds every tick and compounds over minutes. What can still shift things is the browser throttling a tab in the background, so leave it visible if the timing matters.

Does it make a sound?+

Where a sound makes sense, it is generated with the Web Audio API rather than loaded as a file, so there is nothing to download and nothing to block. Browsers refuse to start audio until you have interacted with the page, which is why the first press is what switches it on.

Can I use HTTP Headers Reference on a phone?+

Yes. The controls are sized for touch and the layout collapses to one column on a narrow screen. Bear in mind that a phone locking its screen will suspend the page, and timing stops with it.