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HTTP Header Parser

Paste raw HTTP headers and get them parsed, explained and checked.

Quick Tool Overview

The HTTP Header Parser turns a pasted header block into a readable table, pulls apart the start line, comments on the security headers, flags version leaks and calls out duplicates that matter.

What it does
Parses and reviews raw HTTP headers
You give it
A block of request or response headers
You get back
A parsed table with security and duplicate notes
Best for
Auditing a response and debugging caching or CORS
Developer Tools Free, unlimited use No sign-up Runs in your browser

About the HTTP Header Parser

Copy a block of headers out of your browser's network panel or a curl -I output and paste it here. They are parsed into a readable table, with the start line pulled apart into its method and target, or its status code and reason.

Beyond formatting, the parser comments. Security headers are noted as present or missing — Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options, Referrer-Policy. Headers that leak version information, such as Server and X-Powered-By, are flagged. Duplicates are called out, because a repeated Set-Cookie is normal and a repeated Content-Length is a request-smuggling risk. Folded continuation lines are rejoined the way a server would.

Key features of the HTTP Header Parser

Security headers assessed

HSTS, CSP, nosniff and Referrer-Policy are reported as present or missing, rather than simply listed if they happen to be there.

Version leaks flagged

Server and X-Powered-By tell an attacker exactly what to target, and the parser says so.

Duplicates called out

A repeated Set-Cookie is normal; a repeated Content-Length is a request-smuggling risk. Both are surfaced.

Start line decoded

A status line gets its code explained, a request line its method and target separated.

Folded lines rejoined

Obsolete continuation lines are joined the way a server would read them, so a wrapped header is not misread.

How to use the HTTP Header Parser

  1. 1

    Paste the headers

    From developer tools, curl -I, or a raw request log.

  2. 2

    Read the start line

    A status line shows the code and its meaning; a request line shows the method and target.

  3. 3

    Check the security notes

    Missing protections and version-leaking headers are both called out.

  4. 4

    Look at the duplicates

    Repeated headers are listed, since some are fine and some are a problem.

Frequently asked questions

In Chrome or Firefox developer tools, open the Network tab, click a request and use "Copy response headers" or "Copy request headers". On the command line, curl -I gives you response headers directly.

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