HTTPRef
HTTP Status Codes, Headers and MIME Types Reference
Learn HTTP status codes, headers, and MIME types with clear examples, common errors, and practical fixes for developers.
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HTTP Status Codes
Understand response codes like 200, 404, 429, and 500.
Browse status codes →
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HTTP Headers
Learn what headers like Authorization and Content-Type do.
Browse headers →
64
MIME Types
Browse common MIME types for APIs, files, and browsers.
Browse MIME types →
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Why HTTPRef
Dev-first explanations
No academic jargon. Every entry is written to answer real questions developers run into.
Practical examples
Syntax, real HTTP examples, common mistakes, and the context you need to actually use it.
Fast and searchable
Find what you need instantly across status codes, headers, and MIME types. No ads, no popups, no fluff.
Frequently asked questions
What does HTTP 404 mean?
404 Not Found means the server could not find the requested resource. It usually means the URL is wrong, the page was deleted, or the route does not exist.
See 404 Not Found →What is the difference between 401 and 403?
401 Unauthorized means the client is not authenticated — credentials are missing or invalid. 403 Forbidden means the client is authenticated but does not have permission to access the resource.
See 401 Unauthorized →What causes a CORS error?
CORS errors occur when a browser blocks a cross-origin request because the server did not include the correct Access-Control-Allow-Origin header in its response.
See Access-Control-Allow-Origin →What is the Content-Type header?
Content-Type tells the browser or API client what format the response body is in — for example application/json for JSON data or text/html for HTML pages.
See Content-Type →What is HTTP 429?
429 Too Many Requests means the client has sent too many requests in a given time and has been rate limited. The server may include a Retry-After header indicating when to retry.
See 429 Too Many Requests →What is application/json?
application/json is the MIME type used when sending or receiving JSON data over HTTP. It is the standard Content-Type for REST API requests and responses.
See application/json →