HTTP Status Code Reference
Search HTTP response codes and see plain-English meanings with common causes.
100
1xx Informational
Continue
Request headers received; continue sending body.
Common cause: Large upload request accepted by server.
101
1xx Informational
Switching Protocols
Server is switching protocols (e.g. WebSocket).
Common cause: Upgrade header in handshake flow.
200
2xx Success
OK
Request succeeded and response includes requested data.
Common cause: Normal successful API/page request.
201
2xx Success
Created
Resource created successfully.
Common cause: POST endpoint creating a record.
204
2xx Success
No Content
Request succeeded but response body is empty.
Common cause: DELETE or update endpoint with no response payload.
301
3xx Redirection
Moved Permanently
Resource has a permanent new URL.
Common cause: Domain or URL migration with redirect.
302
3xx Redirection
Found
Resource temporarily available at another URL.
Common cause: Temporary redirect after auth or flow checks.
304
3xx Redirection
Not Modified
Cached version is still valid; no body returned.
Common cause: Conditional request with ETag/If-Modified-Since.
400
4xx Client Error
Bad Request
Request is malformed or invalid.
Common cause: Invalid JSON, missing required fields, wrong params.
401
4xx Client Error
Unauthorized
Authentication required or token invalid.
Common cause: Missing/expired auth token.
403
4xx Client Error
Forbidden
Authenticated but not allowed to access resource.
Common cause: Role/permission check failed.
404
4xx Client Error
Not Found
Requested resource does not exist.
Common cause: Wrong URL, deleted resource, or bad route.
405
4xx Client Error
Method Not Allowed
HTTP method is not supported on this route.
Common cause: Sending POST to a GET-only endpoint.
409
4xx Client Error
Conflict
Request conflicts with current resource state.
Common cause: Duplicate unique value or edit race conflict.
410
4xx Client Error
Gone
Resource existed before but is permanently removed.
Common cause: Old endpoint intentionally retired.
413
4xx Client Error
Payload Too Large
Request body exceeds allowed size.
Common cause: Upload exceeds server/body parser limits.
415
4xx Client Error
Unsupported Media Type
Server does not support request content type.
Common cause: Wrong Content-Type header (e.g. text/plain vs application/json).
422
4xx Client Error
Unprocessable Content
Request syntax is valid but semantic validation fails.
Common cause: Business validation error, invalid field format, failed schema constraints.
429
4xx Client Error
Too Many Requests
Rate limit exceeded.
Common cause: Burst traffic or repeated API calls.
500
5xx Server Error
Internal Server Error
Unexpected server-side failure occurred.
Common cause: Unhandled exception in application code.
502
5xx Server Error
Bad Gateway
Proxy/gateway got invalid upstream response.
Common cause: Upstream service unavailable or returned malformed response.
503
5xx Server Error
Service Unavailable
Server temporarily unavailable.
Common cause: Maintenance window, overload, or dependency outage.
504
5xx Server Error
Gateway Timeout
Gateway timed out waiting for upstream.
Common cause: Slow downstream service or network timeout.
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