Request Header Inspector

Server assisted API Testing

Instantly view your own browser's request headers (User-Agent, Accept, language, client hints) or capture headers from any client via a unique URL, with plain-language explanations.

Privacy: Captured requests are held on the Mutqan backend for two hours and then deleted. The capture URL itself expires at most 24 hours after it is created; the SMS Delivery Inspector deletes its URL when you leave, reload or close the page, as the other capture tools do when the browser blocks session storage. No mailbox or address is created for you. Credentials such as Authorization headers are never stored. Do not point production traffic containing personal data at it.

What are HTTP headers?

HTTP headers are the name: value lines that travel with a request or a response and describe it — the content type and length, caching rules, authentication, the accepted languages, cookies, and security policies. RFC 9110 defines the standard fields; a header names are case-insensitive, values are not, and the same header may appear more than once.

How to use Request Header Inspector

  1. Open the tool — your browser headers load automatically.
  2. To inspect another client, create a capture URL and send a request from it.
  3. Select the captured request and read the Headers tab.

Request Header Inspector features

  • Shows your own browser request headers instantly, with a plain-language explanation for each
  • Capture headers sent by any other client through a unique URL
  • Headers grouped by purpose with meanings (User-Agent, Accept, Accept-Language, client hints, Sec-Fetch-*, cookies…)
  • Network headers added by the edge (cf-*, x-forwarded-*) identified separately
  • Copy all headers as text

Request Header Inspector example

Your browser headers

Input:

(automatic GET /api/v1/echo)

Output:

user-agent: Mozilla/5.0 … Chrome/128 — Identifies the browser and OS
accept-language: ar-SA,ar;q=0.9,en;q=0.8 — Preferred languages for content negotiation
sec-fetch-mode: cors — How the request was initiated

Frequently asked questions about Request Header Inspector

How do I see my own headers?

They load automatically at the top of the page through the echo endpoint, with an explanation for each header (User-Agent, Accept, language, client hints, Sec-Fetch-* and more).

How do I inspect headers from another client?

Create a capture URL and send a request from that client; select it in the list to see its headers, grouped and explained.

Why do I see Cloudflare or forwarding headers?

Requests pass through the edge network before reaching the server, and cf-* and x-forwarded-* headers are added on the way. Your own browser headers show them under Network. Captured requests never record cf-* headers, so only headers such as x-forwarded-* appear there.

References

  • RFC 9110: HTTP SemanticsIETF · 2022The meaning of HTTP methods, header fields, status codes and content negotiation, independent of the wire version.
  • HTTP headers — MDNMDN Web Docs (Mozilla)Reference for request and response headers: syntax, directives and browser support.
  • OWASP Cheat Sheet Series: HTTP HeadersOWASP FoundationWhich security headers to send (HSTS, CSP, X-Content-Type-Options, frame protection) and which to remove (Server, X-Powered-By).
  • RFC 9421: HTTP Message SignaturesIETF · 2024A standard way to sign HTTP messages so a receiver can verify their origin and integrity — the basis of modern webhook signatures.