HTTP Headers Reference
A searchable reference of common HTTP headers and what they do, for both requests and responses.
| Header | Purpose |
|---|---|
No matches.
About this tool
A searchable reference of common HTTP headers and what they do, for both requests and responses.
Privacy
This tool runs entirely in your browser. Your data is processed locally and never uploaded to a server.
How to use this tool
- Type a header name, such as Authorization or Cache-Control, into the search box.
- Read the matching entry to see whether the header is used in a request or a response.
- Check the plain-language description to understand what the header is for and when it matters.
- Use the worked example to see how the header appears in real HTTP traffic.
Step by step, what happens
- The tool takes the header name you enter and searches its built-in reference list.
- It filters the list to headers that match your query, usually by exact name or close match.
- For each match, it shows the header direction, meaning request, response, or both.
- It then displays a short explanation of the header's purpose in HTTP.
- If the header has an example, the tool shows how it would typically be used in practice.
Worked example
A common case is checking what the Cache-Control response header means when you see it in browser dev tools.
Input: Cache-Control
- You search for Cache-Control in the reference.
- The tool returns the header entry and marks it as a response header, while noting that it can also appear in requests.
- You read the description to learn that it controls caching behavior for clients, proxies, and browsers.
Output: Cache-Control
Type: Request or response header
Purpose: Controls how caching works for a resource, such as whether it can be stored, reused, or must be revalidated.
Tips and common mistakes
- Search the exact header name if you know it, because short partial terms can return several related headers.
- Pay attention to whether the header is for requests, responses, or both, since the meaning can change by direction.
- Do not assume a familiar name means the same thing in every context, because some headers are only meaningful in specific HTTP flows.
- Use the worked example to connect the header name to a real use case, especially when reading browser or server logs.
Frequently asked questions
What is the difference between request and response headers?
Request headers are sent by the client; response headers are returned by the server. Some can appear in both.
What does Cache-Control do?
It tells browsers and proxies how and how long to cache a response.
What is CORS?
A browser security mechanism controlled by Access-Control-* headers that governs cross-origin requests.
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