HTTP Headers Reference
Look up HTTP header fields and their meanings with our comprehensive free HTTP Headers Reference. Browse and search through response headers, request headers, and common header categories including caching, security, content negotiation, and CORS headers. Each header entry includes a detailed description, syntax specification, practical examples, allowed values, and relevant RFC references. This reference guide is essential for backend developers configuring server responses, frontend developers debugging CORS issues, DevOps engineers setting up reverse proxies, and security professionals hardening HTTP configurations. Search by header name or filter by category to find exactly what you need.
What Is
The HTTP Headers Reference is a comprehensive, searchable knowledge base of HTTP header fields organized by category and function. It covers all standard HTTP headers including: General headers (Cache-Control, Connection, Date, Trailer, Transfer-Encoding, Upgrade, Via, Warning), Request headers (Accept, Accept-Charset, Accept-Encoding, Accept-Language, Authorization, Cookie, Expect, From, Host, If-Match, If-Modified-Since, If-None-Match, If-Range, If-Unmodified-Since, Max-Forwards, Proxy-Authorization, Range, Referer, TE, User-Agent), Response headers (Accept-Ranges, Age, ETag, Location, Proxy-Authenticate, Retry-After, Server, Vary, WWW-Authenticate), Entity headers (Allow, Content-Encoding, Content-Language, Content-Length, Content-Location, Content-MD5, Content-Range, Content-Type, Expires, Last-Modified), and Security headers (Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options, X-Frame-Options, X-XSS-Protection, Referrer-Policy, Permissions-Policy). Each entry provides description, syntax, directives, examples, and browser compatibility.
How to Use
- Open the HTTP Headers Reference in your browser — no installation or registration needed.
- Browse headers by category using the navigation tabs: Security, Caching, Content, CORS, and All.
- Use the search bar to quickly find a specific header by name.
- Click on any header to expand its full reference page with detailed description and syntax.
- Review the practical examples showing correct header usage and common configurations.
- Copy the example configurations directly for use in your server setup.
Examples
Input: Header: Content-Type: application/json
Process: Identify header category (Response) → Explain purpose → Show syntax
Result: Tells the client the media type of the response body (JSON)
Input: Header: Cache-Control: max-age=3600, public
Process: Parse directive values → Calculate TTL → Cache behavior
Result: Response cached for 3600s (1hr), shared across users
Related Searches
People also search for: http, headers, reference, response, request, http headers reference.
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Frequently Asked Questions
Is the HTTP Headers Reference free to use?
Yes, this reference tool is completely free with full access to all header entries, no registration required, and no premium features. All content is available immediately, and you can browse, search, and copy information without any restrictions or costs.
How often is the reference updated?
The reference is regularly updated to include new HTTP headers, updated RFC specifications, and current browser compatibility information. We monitor IETF RFC publications, WHATWG specifications, and W3C recommendations to ensure the information stays current with evolving web standards.
What are the most important security headers?
The most critical security headers include: Content-Security-Policy (CSP) for preventing XSS and injection attacks, Strict-Transport-Security (HSTS) for enforcing HTTPS, X-Content-Type-Options to prevent MIME type sniffing, X-Frame-Options (or CSP frame-ancestors) for clickjacking prevention, Referrer-Policy for controlling referrer information leakage, and Permissions-Policy for restricting browser feature access.
Can I search for a specific header?
Yes, use the search bar at the top of the reference page to quickly find any header by name. The search is case-insensitive and matches partial header names, making it easy to find what you are looking for even if you only remember part of the name.
Does the reference cover custom or non-standard headers?
The reference primarily focuses on standard HTTP headers defined by RFC specifications and W3C/WHATWG standards. Common non-standard headers (like X- prefixed legacy headers) are included where they are widely used. For truly custom headers used by specific APIs, consult the API documentation.
Are the header examples production-ready?
The examples are educational starting points that demonstrate correct header syntax and common configurations. For production use, particularly security headers, always review and customize the values for your specific application requirements. CSP policies especially need careful testing to avoid breaking legitimate functionality.