HTTP Headers Reference

What Are HTTP Headers?

HTTP headers are key-value pairs sent in HTTP requests and responses. They provide metadata about the message, controlling caching, authentication, content type, CORS behavior, security policies, and more. Understanding common headers is essential for web development, API integration, and debugging.

How to Use This Reference

1. Search: Type a header name (e.g., “Authorization”, “Cache-Control”) in the search box
2. Filter: Choose a category (Auth, Cache, CORS, Security, Content) to narrow results
3. Browse Tabs: Switch between Request, Response, or General headers
4. Copy: Click any header name to copy it to your clipboard
5. Learn: Read the description and example value for each header

Common Use Cases

• API Development: Use headers like Content-Type and Authorization for secure endpoints
• Performance Optimization: Implement caching with Cache-Control and ETag
• Security: Configure CORS with Access-Control-Allow-* headers
• Debugging: Check response headers to understand content negotiation and server behavior
• Cross-Origin Requests: Handle CORS preflight requests and responses

Frequently Asked Questions

What’s the difference between Request and Response headers?

Request headers are sent by the client (browser) to the server, containing information like the requested resource and authentication. Response headers are sent by the server back to the client, containing information about the response (content type, caching rules, etc.).

What does “General” headers mean?

General headers can appear in both HTTP requests and responses. They apply to the entire message regardless of direction, such as Date and Connection.

What are deprecated headers?

Deprecated headers are no longer recommended for use due to security concerns, obsolescence, or replacement by better alternatives. They’re marked with a warning badge. Avoid using them in new applications, but recognize them when debugging legacy systems.

How do I use the search and filter?

The search box finds headers by name (partial match). The category filter narrows results to specific types (Auth, Cache, CORS, Security, Content). You can use both together to quickly locate what you need.

Can I copy header names?

Yes! Click on any header name (the monospace text) to copy it to your clipboard. A confirmation message will appear at the bottom right.

Where can I find the official specification?

Each header includes a link to its official RFC or MDN documentation. Click the spec link to learn more about technical details, allowed values, and usage examples from authoritative sources.