HTTP Status Codes — Complete Reference List

Every HTTP response begins with a three-digit status code that tells you, before you read a single byte of the body, whether the request worked. The first digit sets the category: 2xx succeeded, 4xx means your request was wrong, and 5xx means the server failed. Reading it correctly is the first step in debugging any API call — you can check it for any endpoint with the API tester.

1xx — Informational

The request was received and the process is continuing. These are interim responses you rarely handle directly.

Code	Meaning
`100` Continue	The server received the request headers and the client should proceed to send the request body.
`101` Switching Protocols	The server is switching to a different protocol as requested by the client's Upgrade header.
`102` Processing	The server has accepted the request but has not yet completed it.
`103` Early Hints	The server is sending preliminary headers, typically Link headers for preloading, before the final response.

2xx — Success

The request was received, understood and accepted.

Code	Meaning
`200` OK	The request succeeded and the response body contains the result.
`201` Created	The request succeeded and a new resource was created as a result.
`202` Accepted	The request was accepted for processing, but the processing has not finished.
`204` No Content	The request succeeded and there is deliberately no response body.
`206` Partial Content	The server is delivering only part of the resource, as requested by a Range header.

3xx — Redirection

Further action is needed to complete the request, usually following a different URL.

Code	Meaning
`300` Multiple Choices	The resource has more than one representation, and the server is leaving the choice to the client.
`301` Moved Permanently	The resource has permanently moved to the URL in the Location header.
`302` Found	The resource is temporarily at a different URL, but future requests should still use the original.
`303` See Other	The response to the request can be found at another URL, and should be retrieved with GET.
`304` Not Modified	The cached copy the client already has is still valid, so no body is sent.
`307` Temporary Redirect	Like 302, but the HTTP method and body must be preserved when following the redirect.
`308` Permanent Redirect	Like 301, but the method and body must be preserved.

4xx — Client Error

The request contains bad syntax or cannot be fulfilled. Something about the request needs to change.

Code	Meaning
`400` Bad Request	The server could not understand the request because it is malformed.
`401` Unauthorized	The request lacks valid authentication credentials. Despite the name, this means unauthenticated.
`402` Payment Required	The request cannot be processed until payment is made.
`403` Forbidden	The server understood the request and knows who you are, but refuses to authorise it.
`404` Not Found	The server cannot find the requested resource.
`405` Method Not Allowed	The endpoint exists but does not support the HTTP method you used.
`406` Not Acceptable	The server cannot produce a response matching the client's Accept header.
`407` Proxy Authentication Required	A proxy between you and the server wants credentials before it will forward the request.
`408` Request Timeout	The server timed out waiting for the client to finish sending the request.
`409` Conflict	The request conflicts with the current state of the resource.
`410` Gone	The resource was deliberately removed and will not come back.
`411` Length Required	The server refuses the request because it does not specify a Content-Length header.
`412` Precondition Failed	A condition the client set in the request headers evaluated to false on the server.
`413` Payload Too Large	The request body is larger than the server is willing to process.
`414` URI Too Long	The URL is longer than the server is willing to process.
`415` Unsupported Media Type	The request body is in a format the endpoint does not accept.
`416` Range Not Satisfiable	The Range header asks for a part of the resource that does not exist.
`417` Expectation Failed	The server cannot meet the requirement stated in the request's Expect header.
`418` I'm a teapot	The server refuses to brew coffee because it is, permanently, a teapot. An April Fools' joke that became a reserved status code.
`419` Page Expired	The request failed the CSRF check: its token was missing, wrong, or belonged to a session that has ended.
`421` Misdirected Request	The request reached a server that is not configured to answer for that host name.
`422` Unprocessable Entity	The syntax is valid but the content fails the server's validation rules.
`423` Locked	The resource you are trying to change is locked.
`424` Failed Dependency	The request failed because it depended on another action, and that action failed.
`425` Too Early	The server will not process a request that arrived in TLS early data, because it could be a replay.
`426` Upgrade Required	The server refuses to answer over the current protocol and names the one it wants instead.
`428` Precondition Required	The server requires the request to be conditional.
`429` Too Many Requests	You have sent too many requests in a given amount of time and are being rate limited.
`431` Request Header Fields Too Large	The server refuses to process the request because its headers are too large.
`451` Unavailable For Legal Reasons	The resource is unavailable because of a legal demand.
`499` Client Closed Request	The client closed the connection before the server had finished responding.

5xx — Server Error

The server failed to fulfil an apparently valid request. The problem is on the server side.

Code	Meaning
`500` Internal Server Error	The server hit an unexpected condition and could not complete the request.
`501` Not Implemented	The server does not support the functionality required to fulfil the request.
`502` Bad Gateway	A server acting as a gateway or proxy received an invalid response from the upstream server.
`503` Service Unavailable	The server is temporarily unable to handle the request.
`504` Gateway Timeout	A gateway or proxy did not receive a timely response from the upstream server.
`505` HTTP Version Not Supported	The server does not support the major HTTP version named in the request.
`507` Insufficient Storage	The server cannot store the representation needed to complete the request.
`508` Loop Detected	The server found an infinite loop while processing the request and stopped.
`509` Bandwidth Limit Exceeded	The site has used up the data transfer its hosting plan allows.
`511` Network Authentication Required	The network you are on wants you to sign in before it will let traffic through.
`520` Web Server Returned an Unknown Error	Cloudflare reached the origin server and got back something it could not interpret as a valid HTTP response.
`521` Web Server Is Down	Cloudflare tried to connect to the origin server and the connection was refused.
`522` Connection Timed Out	Cloudflare tried to open a TCP connection to the origin server and got no answer in time.
`523` Origin Is Unreachable	Cloudflare could not find a network route to the origin server.
`524` A Timeout Occurred	Cloudflare connected to the origin server, but the origin took too long to send a response.
`525` SSL Handshake Failed	Cloudflare could not complete a TLS handshake with the origin server.
`526` Invalid SSL Certificate	Cloudflare could not validate the TLS certificate presented by the origin server.

Debugging by status code class

A 4xx means the fix is in your request: check the method, the URL, the headers and the body. The most common culprits are a missing Content-Type, a malformed Authorization header, or a typo in the path.

A 5xx means the fix is on the server, and resending the identical request usually will not help. Capture the exact request that reproduces it — the API tester's Copy as cURL button gives you something you can hand straight to whoever owns the API.