An index of error codes with easy to understand translations.

4XX Errors

(You have an error.)

400 Bad Request
Request cannot be fulfilled due to bad syntax
401 Unauthorized
Authentication is possible but has failed
402 Payment Required
Payment required, reserved for future use
403 Forbidden
Server refuses to respond to request
404 Not Found
Requested resource could not be found
405 Method Not Allowed
Request method not supported by that resource
406 Not Acceptable
Content not acceptable according to the Accept headers
407 Proxy Authentication Required
Client must first authenticate itself with the proxy
408 Request Timeout
Server timed out waiting for the request
409 Conflict
Request could not be processed because of conflict
410 Gone
Resource is no longer available and will not be available again
411 Length Required
Request did not specify the length of its content
412 Precondition Failed
Server does not meet request preconditions
413 Request Entity Too Large
Request is larger than the server is willing or able to process
414 Request-URI Too Long
URI provided was too long for the server to process
415 Unsupported Media Type
Server does not support media type
416 Requested Range Not Satisfiable
Client has asked for unprovidable portion of the file
417 Expectation Failed
Server cannot meet requirements of Expect request-header field
419 Page Expired (Laravel Framework) Unofficial
Used by the Laravel Framework when a CSRF Token is missing or expired.
422 Unprocessable Entity
Request unable to be followed due to semantic errors
423 Locked
Resource that is being accessed is locked
424 Failed Dependency
Resource that is being accessed is locked
426 Upgrade Required
Client should switch to a different protocol
428 Precondition Required
Origin server requires the request to be conditional
429 Too Many Requests
User has sent too many requests in a given amount of time
430 Request Header Fields Too Large (Shopify) Unofficial
Used by Shopify, instead of the 429 Too Many Requests response code, when too many URLs are requested within a certain time frame.
431 Request Header Fields Too Large
Server is unwilling to process the request
440 Login Time-out (Microsoft IIS) Unofficial
The client's session has expired and must log in again.
444 No Response (nginx)
Used internally[89] to instruct the server to return no information to the client and close the connection immediately.
449 Retry With (Microsoft IIS) Unofficial
The server cannot honour the request because the user has not provided the required information.
450 Blocked by Windows Parental Controls (Microsoft) Unofficial
The Microsoft extension code indicated when Windows Parental Controls are turned on and are blocking access to the requested webpage.
451 Redirect (Microsoft IIS) Unofficial
Used in Exchange ActiveSync when either a more efficient server is available or the server cannot access the users' mailbox. The client is expected to re-run the HTTP AutoDiscover operation to find a more appropriate server.
460 (Amazon AWS) Unofficial
463 (Amazon AWS) Unofficial
498 Invalid Token (Esri) Unofficial
Returned by ArcGIS for Server. Code 498 indicates an expired or otherwise invalid token.
494 Request header too large (nginx) Unofficial
Client sent too large request or too long header line.
495 SSL Certificate Error (nginx) Unofficial
An expansion of the 400 Bad Request response code, used when the client has provided an invalid client certificate.
496 SSL Certificate Required (nginx) Unofficial
An expansion of the 400 Bad Request response code, used when a client certificate is required but not provided.
497 HTTP Request Sent to HTTPS Port (nginx) Unofficial
An expansion of the 400 Bad Request response code, used when the client has made a HTTP request to a port listening for HTTPS requests.
499 Client Closed Request (nginx) Unofficial
Used when the client has closed the request before the server could send a response.
499 Token Required (Esri) Unofficial
Returned by ArcGIS for Server. Code 499 indicates that a token is required but was not submitted.

5XX Errors

(The server has an error.)

500 Internal Server Error
Generic error message
501 Not Implemented
Server does not recognise method or lacks ability to fulfill
502 Bad Gateway
Server received an invalid response from upstream server
503 Service Unavailable
Server is currently unavailable
504 Gateway Timeout
Gateway did not receive response from upstream server
505 HTTP Version Not Supported
Server does not support the HTTP protocol version
506 Variant Also Negotiates (Experimental)
Content negotiation for the request results in a circular reference
507 Insufficient Storage
Server is unable to store the representation
508 Loop Detected
Server detected an infinite loop while processing the request
509 Bandwidth Limit Exceeded Unofficial
The server has exceeded the bandwidth specified by the server administrator; this is often used by shared hosting providers to limit the bandwidth of customers.
510 Not Extended
Further extensions to the request are required
511 Network Authentication Required
Client needs to authenticate to gain network access
520 Web server is returning an unknown error
521 Web server is down
The server is powered off. Perhaps in the middle of rebooting.
522 Connection timed out
Due to the high usage of Cloudflare, the 522 connection timed out error is one of the most common browser error messages
523 Origin Unreachable
524 Timeout
The server is not responding. It probably needs rebooting.
525 SSL handshake failed
526 Invalid SSL certificate Unofficial
Used by Cloudflare and Cloud Foundry's gorouter to indicate failure to validate the SSL/TLS certificate that the origin server presented.
529 Site is overloaded Unofficial
Used by Qualys in the SSLLabs server testing API to signal that the site can't process the request.
530 Site is frozen Unofficial
Used by the Pantheon web platform to indicate a site that has been frozen due to inactivity.
598 Network read timeout error Unofficial
Used by some HTTP proxies to signal a network read timeout behind the proxy to a client in front of the proxy.

1XXX Cloudflare Errors

Specific to domains proxied by Cloudflare.

Error 1000
DNS points to prohibited IP
Error 1001
DNS resolution error
Error 1002
DNS points to Prohibited IP
Error 1002
Error 1003
ccess Denied: Direct IP Access Not Allowed
Error 1004
Host Not Configured to Serve Web Traffic
Error 1006
1007, and 1008 Access Denied: Your IP address has been banned
Error 1010
The owner of this website has banned your access based on your browser's signature
Error 1011
Access Denied (Hotlinking Denied)
Error 1012
Access Denied
Error 1013
HTTP hostname and TLS SNI hostname mismatch
Error 1014
CNAME Cross-User Banned
Error 1015
You are being rate limited
Error 1016
Origin DNS error
Error 1018
Could not find host
Error 1019
Compute server error
Error 1020
Access denied
Error 1025
Please check back later
Error 1101
Rendering error
Error 1102
Rendering error
Error 1200
Cache connection limit