URLError codes returned by URL loading APIs

URLError are part of the Foundation framework, commonly used for network requests. When something goes wrong during a network task, URLSession provides an NSError object that can contain URLError codes. These error codes belong to the URLError.Code enumeration.

Below is a list of URLError error codes with their meanings:

Error category	Error	Code	Meaning
Connection	`cancelled`	-999	The task was explicitly canceled, usually by the app
	`badURL`	-1000	The provided URL is malformed or invalid.
	`unsupportedURL`	-1002	The URL scheme is not supported
	`cannotFindHost`	-1003	The host name could not be resolved
	`cannotConnectToHost`	-1004	The connection to the host failed
	`networkConnectionLost`	-1005	The network connection was lost during the request
	`dnsLookupFailed`	-1006	The DNS lookup failed
	`httpTooManyRedirects`	-1007	Too many HTTP redirects were encountered
	`resourceUnavailable`	-1008	The requested resource is unavailable
	`notConnectedToInternet`	-1009	The device is not connected to the Internet
	`redirectToNonExistentLocation`	-1010	The request redirected to a nonexistent location
	`badServerResponse`	-1011	The server returned an invalid or unexpected response
	`userCancelledAuthentication`	-1012	The user canceled authentication
	`userAuthenticationRequired`	-1013	Authentication is required to access the resource
	`zeroByteResource`	-1014	The resource’s data is zero bytes
	`cannotDecodeRawData`	-1015	The raw data could not be decoded
	`cannotDecodeContentData`	-1016	The content data could not be decoded
	`cannotParseResponse`	-1017	The response data could not be parsed
Certificate	`appTransportSecurityRequiresSecureConnection`	-1022	App Transport Security (ATS) requires a secure connection
	`secureConnectionFailed`	-1200	The SSL/TLS handshake failed
	`serverCertificateHasBadDate`	-1201	The server’s certificate has an invalid date
	`serverCertificateUntrusted`	-1202	The server’s certificate is untrusted
	`serverCertificateHasUnknownRoot`	-1203	The server’s certificate has an unknown root authority
	`serverCertificateNotYetValid`	-1204	The server’s certificate is not yet valid
	`clientCertificateRejected`	-1205	The server rejected the client certificate
	`clientCertificateRequired`	-1206	The server requires a client certificate
Download	`cannotLoadFromNetwork`	-2000	The resource cannot be loaded from the network
	`cannotCreateFile`	-3000	Failed to create a file on disk
	`cannotOpenFile`	-3001	Failed to open a file on disk
	`cannotCloseFile`	-3002	Failed to close a file on disk
	`cannotWriteToFile`	-3003	Failed to write to a file on disk
	`cannotRemoveFile`	-3004	Failed to remove a file on disk
	`cannotMoveFile`	-3005	Failed to move a file on disk
	`downloadDecodingFailedMidStream`	-3006	Download decoding failed during the stream
	`downloadDecodingFailedToComplete`	-3007	Download decoding failed to complete
Timeout	`timedOut`	-1001	The request timed out
Background Task	`backgroundSessionRequiresSharedContainer`	-995	A background session requires a shared container
	`backgroundSessionInUseByAnotherProcess`	-996	The background session is in use by another process
	`backgroundSessionWasDisconnected`	-997	The background session was disconnected