HTTP Status Code Explainer

200 OK

Request succeeded. Response body contains the representation of the resource.

201 Created

Request succeeded and a new resource was created. Location header often contains the new URL.

204 No Content

Request succeeded but there is no body to return (e.g. after a successful DELETE).

301 Moved Permanently

Resource has a new permanent URL. Use the Location header. Clients should update bookmarks.

302 Found

Temporary redirect. Use the Location header. Method may change to GET.

304 Not Modified

Cached response is still valid. Used with conditional requests (If-None-Match, If-Modified-Since).

400 Bad Request

Server could not understand the request (syntax, invalid JSON, validation failed).

• Check request body format (JSON/form).
• Validate required fields and types.
• Check URL and query parameters.

401 Unauthorized

Authentication required or failed. Provide valid credentials (e.g. Bearer token).

• Include Authorization header.
• Ensure token is not expired.
• Use correct auth scheme (Bearer, Basic).

403 Forbidden

Server understood the request but refuses to authorize it. Identity may be known but not allowed.

• Check user/role permissions.
• Verify resource ownership or scope.
• Review API key or scope.

404 Not Found

Resource does not exist at this URL or has been removed.

• Verify URL path and IDs.
• Check if resource was deleted.
• Confirm correct environment (staging vs prod).

405 Method Not Allowed

HTTP method is not supported for this resource. Allow header lists allowed methods.

409 Conflict

Request conflicts with current state (e.g. duplicate create, version conflict).

422 Unprocessable Entity

Request is well-formed but semantic validation failed (e.g. business rules).

429 Too Many Requests

Rate limit exceeded. Retry-After header may indicate when to retry.

500 Internal Server Error

Unexpected server error. No actionable fix on client; retry or contact API owner.

• Retry with exponential backoff.
• Check API status page.
• Report if persistent.

502 Bad Gateway

Server acting as gateway got an invalid response from upstream.

503 Service Unavailable

Server temporarily overloaded or down. Retry-After may be provided.