What are HTTP headers?
HTTP headers are metadata fields sent with requests and responses. They help servers understand what the client wants and can also reveal clues about the browser, proxies, or security layers involved.
- What common headers mean.
- Why headers are useful for troubleshooting.
- What headers do and do not reveal about your network.
Common headers
Headers such as User-Agent, Accept-Language, and Referer provide context for the request.
Some reverse proxies add forwarding headers that help operators understand where traffic came from.
Why they matter
Header mismatches help spot proxying, app misconfiguration, caching mistakes, and origin issues.
They are also useful when debugging bot behavior or browser-specific bugs.
Privacy angle
Headers can expose browser type, language preference, and sometimes other session clues.
They do not usually replace network diagnostics, but they complement them.
How WhenIP uses them
The header check shows what the site receives from your current request path.
That helps compare direct access, VPN paths, and mobile or corporate proxies.
Do headers contain my IP address?
Sometimes proxy-related headers do, but the source IP is normally handled separately by the server connection.
Should I trust every forwarding header?
No. Trust depends on whether the proxy chain is controlled and configured correctly.
Last updated: March 29, 2026