HTTP Headers Reference
Searchable reference of common HTTP headers with descriptions.
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Searchable reference of common HTTP headers with descriptions.
Searchable reference of common HTTP headers with descriptions.
Searchable reference of common HTTP headers with descriptions.
| Header | Type | Description |
|---|---|---|
| Accept | Request | Media types the client can accept |
| Accept-Encoding | Request | Acceptable compression encodings (gzip, deflate, br) |
| Accept-Language | Request | Preferred natural language and locale |
| Authorization | Request | Authentication credentials for the request |
| Cache-Control | Both | Directives for caching mechanisms |
| Connection | Both | Control options for the current connection (keep-alive, close) |
| Content-Encoding | Both | Encoding applied to the body (gzip, br) |
| Content-Length | Both | Size of the body in bytes |
| Content-Type | Both | Media type and charset of the body |
| Cookie | Request | HTTP cookies sent by client |
| ETag | Response | Identifier for the resource version |
| Expires | Response | Date/time when the response is stale |
| Host | Request | Domain name and port of the server |
| If-Modified-Since | Request | Conditional: return only if modified after this date |
| If-None-Match | Request | Conditional: return only if ETag does not match |
| Last-Modified | Response | Date/time the resource was last changed |
| Location | Response | URL to redirect the client to |
| Origin | Request | Origin of the cross-origin request |
| Pragma | Both | Implementation-specific directives (legacy) |
| Referer | Request | URL of the referring page |
| Retry-After | Response | How long to wait before retrying a request |
| Server | Response | Software used by the origin server |
| Set-Cookie | Response | Instructs the client to set a cookie |
| Strict-Transport-Security | Response | Enforces HTTPS via HSTS policy |
| Transfer-Encoding | Both | Encoding used to transfer the body (chunked) |
| User-Agent | Request | Browser or client software identifier |
| Vary | Response | Headers that determine cache differentiation |
| WWW-Authenticate | Response | Authentication method required for the resource |
| X-Content-Type-Options | Response | Prevents MIME-type sniffing (nosniff) |
| X-Frame-Options | Response | Controls if the page can be framed |
| X-XSS-Protection | Response | Enables cross-site scripting filter (legacy) |
| Access-Control-Allow-Origin | Response | CORS allowed origin(s) |