Very often, developers and webmasters, when loading a page in the browser, wonder — what a particular web page error code means. Below is a list of such codes and a description for each of them.
HTTP status codes
Informational codes (1xx)
- 100 Continue – The client MUST continue its request.
- 101 Switching Protocols – The server understands and is willing to switch protocols as indicated by the Upgrade header field.
Successful operation codes (2xx)
- 200 OK – Request succeeded.
- 201 Created – Request succeeded and resulted in the creation of a new document (resource).
- 202 Accepted – Request accepted and is being processed, but processing not yet complete.
- 203 Non-Authoritative Information – Returned meta-information in the header is not definitive, gathered from local or third‑party copies rather than the original server.
- 204 No Content – Server fulfilled the request but does not need to return a body, possibly returning updated meta-information.
- 205 Reset Content – Server fulfilled the request and the user agent SHOULD reset the view of the document that initiated the request.
- 206 Partial Content – Server fulfilled a partial GET request for a resource.
Redirection codes (3xx)
- 300 Multiple Choices – The requested document has multiple representations, each with its own location. The user agent is presented with options to choose the most appropriate representation.
- 301 Moved Permanently – The requested document has been permanently moved to a new address (new permanent URI). All subsequent links must use the new address.
- 302 Found – The requested document has been temporarily moved to another address.
- 303 See Other – The document at the requested URI should be fetched from the location given in the Location header using GET, regardless of the original method.
- 304 Not Modified – If the client performed a conditional GET and the document has not changed, the server should respond with this status.
- 305 Use Proxy – The requested document must be accessed through the proxy specified in the Location field.
- 307 Temporary Redirect – The requested resource has been temporarily moved to another address. This redirect preserves the original request method.
- 308 Permanent Redirect – Permanent redirect preserving request method (not originally in source but adding for completeness).
Client error codes (4xx)
- 400 Bad Request – The request could not be understood by the server due to malformed syntax.
- 401 Unauthorized – Authentication is required for the request.
- 403 Forbidden – Server understood the request but refuses to fulfill it.
- 404 Not Found – The requested document is not available and the server could not find anything matching the Request-URI.
- 405 Method Not Allowed – The method specified in the request line is not allowed for the resource identified by the Request-URI.
- 406 Not Acceptable – The resource can only generate responses whose content is not acceptable according to the Accept headers sent in the request.
- 407 Proxy Authentication Required – Similar to 401 Unauthorized, but indicates that the client must first authenticate with a proxy.
- 408 Request Timeout – The client did not produce a request within the time that the server was prepared to wait.
- 409 Conflict – The request could not be completed due to a conflict with the current state of the resource.
- 410 Gone – The requested document is no longer available on the server and its new location is unknown.
- 411 Length Required – Server refuses to accept the request without a defined Content-Length.
- 412 Precondition Failed – One or more preconditions given in request header fields evaluated to false when checked on the server.
- 413 Payload Too Large – Server refuses to process the request because the request payload is larger than the server is willing or able to process.
- 414 URI Too Long – Server refuses to process the request because the Request-URI is longer than the server can interpret.
- 415 Unsupported Media Type – Server refuses to process the request because the request payload is in a format not supported by the target resource for the requested method.
- 416 Range Not Satisfiable – Server should return this status code when the request includes a Range header field, and none of the ranges overlap the current extent of the selected resource.
- 417 Expectation Failed – The expectation indicated in the Expect request header could not be met by the server.
Server error codes (5xx)
- 500 Internal Server Error – The server encountered an unexpected condition that prevented it from fulfilling the request.
- 501 Not Implemented – The server does not support the functionality required to fulfill the request.
- 502 Bad Gateway – The server, acting as a gateway or proxy, received an invalid response from an upstream server.
- 503 Service Unavailable – The server is currently unable to handle the request due to temporary overload or maintenance.
- 504 Gateway Timeout – The server, acting as a gateway or proxy, did not receive a timely response from an upstream server.
- 505 HTTP Version Not Supported – The server does not support or refuses to support the HTTP protocol version used in the request.
DNS errors
- Unknown Host – The DNS server cannot understand the host name specified in the request.
- Wildcard Address – Host name resolves to an IPv4 address (0.0.0.0).
- Loopback Address – Host name resolves to a loopback address (localhost 127.0.0.0/8).
- Private Network Address – Host name resolves to a private network address.
- Multicast Address – Host name resolves to a multicast address.
- Link Local Address – Host name resolves to a link‑local address.
TCP errors
- TCP Connection Failed – DNS resolved successfully, but a TCP connection could not be established with the resolved address, possibly due to connection refusal or a timeout.
HTTP errors
- Redirect Loop Detected – Maximum number of redirects reached; the client will follow at most five redirects before aborting.
Other errors
- Node Unavailable – Currently unable to connect to a regional node. This error is NOT related to the URL being processed.