Inspect the HTTP request headers your browser sends. User-Agent, Accept, and more.
The Request Header Inspector shows the headers that your browser sends with each request—User-Agent, Accept, Accept-Language, and others. Developers use it to debug "wrong content type" or "unsupported format" when the server sees different headers than expected, to copy User-Agent for scripting, or to verify CORS or security headers. Often implemented by sending a request to an echo endpoint that returns the received headers.
DevTools shows the request for a specific resource; the inspector may hit an echo URL. Both are valid; use the one that matches your scenario.
This tool usually shows your real headers. To send custom headers, use the Request Builder.
It tells the server which languages the client prefers; used for content negotiation and localization.
If the echo URL is same-site, cookies are sent automatically; the inspector shows Cookie if present.
Headers may include X-Forwarded-For or similar if behind a proxy; the echo server may log IP for the response.