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HTTP Header Parser

Networking
Paste a full HTTP request, response, or just the headers block. One header per line in Name: Value format.

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About This Tool

HTTP Header Parser – Decode and Understand HTTP Headers

Every HTTP request and response carries a set of headers — key-value metadata fields that control caching, authentication, content negotiation, security policies, and much more. While browsers and servers handle these automatically, understanding what each header does is essential for debugging APIs, hardening web applications, and diagnosing connectivity issues. This HTTP Header Parser takes raw header text and explains every field in plain English so you can quickly understand what is happening in an HTTP exchange.

What Are HTTP Headers?

HTTP headers are defined in a series of RFCs maintained by the IETF. The core HTTP/1.1 header fields are specified in RFC 7230 through RFC 7235. Additional headers are defined by later RFCs for features like cookies (RFC 6265), Cross-Origin Resource Sharing (CORS, Fetch Living Standard), and HTTP security best practices. Each header follows the format Header-Name: value on its own line, with names being case-insensitive by the HTTP specification.

Header Categories Explained

This tool organises HTTP headers into six functional categories:

  • Request headers — Sent by the client to provide context about the request or the client itself. Examples include Host, User-Agent,Accept, Authorization, and Cookie.
  • Response headers — Sent by the server to describe the response or provide instructions to the client. Examples include Server,Location, Set-Cookie, and ETag.
  • General headers — Apply to both requests and responses. Examples include Connection, Date, and Transfer-Encoding.
  • Entity / Representation headers — Describe the body of the message. Examples include Content-Type, Content-Length,Content-Encoding, and Content-Language.
  • Caching headers — Control how responses are stored and reused. Examples include Cache-Control, Expires, Vary, and ETag.
  • Security / CORS headers — Protect users and enforce cross-origin policies. Examples include Strict-Transport-Security,Content-Security-Policy, and the Access-Control-* family.

Common Use Cases

Debugging API Responses

Copy response headers from browser DevTools (Network tab → select a request → Headers section) and paste them into the parser. Instantly see whether caching directives are set correctly, which CORS headers are present, and whether Content-Typeis returning the expected MIME type.

Auditing Security Headers

Paste your server's response headers to check whether critical security headers are in place. The parser highlights Strict-Transport-Security (HSTS),Content-Security-Policy (CSP), X-Content-Type-Options,Referrer-Policy, and Permissions-Policy — all of which are recommended by the OWASP Secure Headers Project. Missing or misconfigured security headers are a common source of web application vulnerabilities.

Learning HTTP

The tool is an excellent learning aid for developers who are new to HTTP. Load one of the built-in samples — a typical GET request, a JSON API response, or a set of security headers — and read the description for each field to understand the role it plays in the HTTP protocol.

Deprecated Headers

The parser flags headers that have been deprecated by the IETF or the browser vendor community. For example:

  • Pragma: no-cache was the HTTP/1.0 way to prevent caching. Replace it with Cache-Control: no-cache.
  • X-Frame-Options has been superseded by theContent-Security-Policy: frame-ancestors directive.
  • X-XSS-Protection is no longer supported in modern browsers and should be removed in favour of a well-configured Content Security Policy.

How to Read the Results

The parser produces a structured table with three columns: the header name and its category badge, the raw value, and a plain-English description of what the header controls. A Deprecated badge appears next to any header that is outdated and should be replaced. The summary section above the table shows the total header count, how many deprecated headers were found, and how headers are distributed across categories.

Privacy and Security

All processing is performed entirely in your browser. Your header data — includingAuthorization tokens, Cookie values, and session information — is never sent to any external server. You can safely paste sensitive headers for analysis without any privacy risk.

Frequently Asked Questions

Is the HTTP Header Parser free?

Yes, HTTP Header Parser is totally free :)

Can I use the HTTP Header Parser offline?

Yes, you can install the webapp as PWA.

Is it safe to use HTTP Header Parser?

Yes, any data related to HTTP Header Parser only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How does the HTTP Header Parser work?

Paste raw HTTP headers — with or without a request or status line — into the input area and click Parse. The tool splits the text line by line, identifies the header name and value on each line, then looks up each header in its built-in database of standard HTTP fields (RFC 7230–7235, RFC 6265, and security-focused RFCs). It displays the name, value, category, and a plain-English description for every header it finds.

What input formats are supported?

The tool accepts standard HTTP/1.1 format where each header is on its own line as 'Name: Value'. You can paste a full HTTP request or response including the request/status line, paste only the headers section, or enter headers copied from browser DevTools. Both CRLF (\r\n) and LF (\n) line endings are handled automatically.

What do the header categories mean?

Headers are grouped into: Request (sent by the client), Response (sent by the server), General (applicable to both), Entity / Representation (describe the message body such as Content-Type and Content-Length), Caching (Cache-Control, ETag, Expires), Security / CORS (HSTS, CSP, X-Content-Type-Options, Access-Control-* headers), and Unknown / Custom for non-standard or proprietary headers.

Which deprecated headers does the tool flag?

Headers marked as deprecated include Pragma (superseded by Cache-Control), Accept-Charset, X-Frame-Options (superseded by CSP frame-ancestors), X-XSS-Protection, Content-MD5, and Warning. The tool labels these clearly so you know to replace them with modern equivalents in new projects.

Can I use this tool to check security headers on my website?

Yes. Copy the response headers from your browser's DevTools (Network tab → select a request → Headers section) and paste them into the tool. The Security / CORS category will highlight which security headers are present and explain what each one does. You can then check for missing headers like Strict-Transport-Security, Content-Security-Policy, and Referrer-Policy.

Does the tool send my headers anywhere?

No. All parsing happens locally in your browser using JavaScript. Your header data is never transmitted to any server, making it safe to paste headers that contain Authorization tokens, cookies, or other sensitive values.