What is the difference between 301 and 302?

301 is a permanent redirect — browsers and search engines cache it and transfer SEO equity to the new URL. 302 is temporary — search engines keep indexing the original URL. Use 301 when you've permanently moved a page.

What is the difference between 401 and 403?

401 Unauthorized means the client needs to authenticate — they might get access if they log in. 403 Forbidden means the server knows who you are but you're not allowed — authenticating won't help.

When should I use 422 vs 400?

Use 400 Bad Request for malformed syntax (invalid JSON, missing headers). Use 422 Unprocessable Content for valid syntax with semantic errors — e.g., a well-formed JSON body that fails business validation.

What does 429 Too Many Requests mean?

The client has exceeded a rate limit. The server response should include a Retry-After header telling the client when to try again. This is the standard code for rate limiting in APIs.

Is 418 a real HTTP status code?

It's real in the sense that it's defined in RFC 2324 as an April Fools' joke — 'I'm a teapot'. It was never intended for production use but is widely implemented as an Easter egg. It won't cause issues if returned, but you shouldn't use it in real APIs.

HTTP Status Codes

Complete reference for every HTTP status code — 1xx through 5xx. Search by number or keyword to find the meaning, use case, and common causes.

1xx

Informational

Request received, continuing process.

2xx

Success

The request was successfully received, understood, and accepted.

3xx

Redirection

Further action needed to complete the request.

4xx

Client Errors

The request contains bad syntax or cannot be fulfilled.

5xx

Server Errors

The server failed to fulfil a valid request.

How to use it

1Type a code number (e.g. 404) or keyword (e.g. 'redirect') in the search box.
2Filter by category using the 1xx–5xx buttons to browse a specific class.
3Click any code card to expand its full explanation.

Common use cases

Quickly look up what a specific HTTP error code means while debugging an API.
Choose the correct status code to return from a REST API endpoint.
Understand 3xx redirect codes and their SEO implications.
Learn the difference between 401 Unauthorized and 403 Forbidden.
Reference 5xx server error codes when diagnosing infrastructure issues.

Frequently asked questions

What is the difference between 301 and 302?: 301 is a permanent redirect — browsers and search engines cache it and transfer SEO equity to the new URL. 302 is temporary — search engines keep indexing the original URL. Use 301 when you've permanently moved a page.
What is the difference between 401 and 403?: 401 Unauthorized means the client needs to authenticate — they might get access if they log in. 403 Forbidden means the server knows who you are but you're not allowed — authenticating won't help.
When should I use 422 vs 400?: Use 400 Bad Request for malformed syntax (invalid JSON, missing headers). Use 422 Unprocessable Content for valid syntax with semantic errors — e.g., a well-formed JSON body that fails business validation.
What does 429 Too Many Requests mean?: The client has exceeded a rate limit. The server response should include a Retry-After header telling the client when to try again. This is the standard code for rate limiting in APIs.
Is 418 a real HTTP status code?: It's real in the sense that it's defined in RFC 2324 as an April Fools' joke — 'I'm a teapot'. It was never intended for production use but is widely implemented as an Easter egg. It won't cause issues if returned, but you shouldn't use it in real APIs.

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