100Continue1xx · Informational
The server got the request headers and the client should send the body.
Typical cause: Used with Expect: 100-continue.
101Switching Protocols1xx · Informational
The server is switching protocols as the client asked.
Typical cause: WebSocket upgrades.
200OK2xx · Success
The request succeeded.
Typical cause: The normal success response.
201Created2xx · Success
The request succeeded and a new resource was created.
Typical cause: After a successful POST/PUT.
202Accepted2xx · Success
The request was accepted but not yet processed.
Typical cause: Async / queued work.
204No Content2xx · Success
Success, but there's no body to return.
Typical cause: Successful DELETE or a beacon.
206Partial Content2xx · Success
Only part of the resource is being sent.
Typical cause: Range requests — video, resumable downloads.
301Moved Permanently3xx · Redirection
The resource has a new permanent URL.
Typical cause: URL changed; update your links. Passes SEO value.
302Found3xx · Redirection
The resource is temporarily at a different URL.
Typical cause: Temporary redirect.
304Not Modified3xx · Redirection
The cached copy is still fresh — use it.
Typical cause: Conditional request with a matching ETag.
307Temporary Redirect3xx · Redirection
Temporary redirect that keeps the HTTP method.
Typical cause: Like 302 but won't switch POST to GET.
308Permanent Redirect3xx · Redirection
Permanent redirect that keeps the method.
Typical cause: Like 301 but preserves POST. (Trailing-slash redirects use this.)
400Bad Request4xx · Client Error
The server couldn't understand the request.
Typical cause: Malformed syntax, bad parameters or JSON.
401Unauthorized4xx · Client Error
You need to authenticate first.
Typical cause: Missing or invalid credentials / token.
403Forbidden4xx · Client Error
You're authenticated but not allowed.
Typical cause: No permission, blocked IP, or WAF rule.
404Not Found4xx · Client Error
The server can't find the resource.
Typical cause: Wrong URL, deleted page, or missing route.
405Method Not Allowed4xx · Client Error
That HTTP method isn't allowed here.
Typical cause: e.g. POST to a GET-only endpoint.
408Request Timeout4xx · Client Error
The client took too long to send the request.
Typical cause: Slow or stalled connection.
409Conflict4xx · Client Error
The request conflicts with the current state.
Typical cause: Edit conflicts, duplicate creates.
410Gone4xx · Client Error
The resource is permanently gone.
Typical cause: Intentionally removed, no forwarding address.
413Payload Too Large4xx · Client Error
The request body is too big.
Typical cause: Upload exceeds the server limit.
418I'm a teapot4xx · Client Error
A joke code from an April Fools' RFC.
Typical cause: Occasionally used for blocked/prank endpoints.
422Unprocessable Entity4xx · Client Error
Syntax is fine but the data failed validation.
Typical cause: Form/validation errors in APIs.
429Too Many Requests4xx · Client Error
You've been rate-limited.
Typical cause: Too many requests in a window — back off and retry.
500Internal Server Error5xx · Server Error
The server hit an unexpected error.
Typical cause: Unhandled exception or bug on the server.
501Not Implemented5xx · Server Error
The server doesn't support that functionality.
Typical cause: Unknown method or unsupported feature.
502Bad Gateway5xx · Server Error
A gateway/proxy got a bad response upstream.
Typical cause: Upstream app down or crashing behind Nginx.
503Service Unavailable5xx · Server Error
The server is temporarily unable to handle the request.
Typical cause: Overloaded, or down for maintenance.
504Gateway Timeout5xx · Server Error
A gateway/proxy timed out waiting upstream.
Typical cause: Upstream too slow to respond.