CURL Errors and Reasons

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Below is the list of all CURL errors and the reasons behind these errors.

Ok Ok

CURL error code 0 – CURLE_OK (0)

All fine. Proceed as usual.

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Unsupported Protocol Unsupported Protocol

CURL error code 1 – CURLE_UNSUPPORTED_PROTOCOL (1)

The URL you passed to libcurl used a protocol that this libcurl does not support. The support might be a compile-time option that you didn’t use, it can be a misspelled protocol string or just a protocol libcurl has no code for.

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Failed Init Failed Init

CURL error code 2 – CURLE_FAILED_INIT (2)

Very early initialization code failed. This is likely to be an internal error or problem, or a resource problem where something fundamental couldn’t get done at init time.

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URL Malfomat URL Malfomat

CURL error code 3 – CURLE_URL_MALFORMAT (3)

The URL was not properly formatted.

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Not Built In Not Built In

CURL error code 4 – CURLE_NOT_BUILT_IN (4)

A requested feature, protocol or option was not found built-in in this libcurl due to a build-time decision. This means that a feature or option was not enabled or explicitly disabled when libcurl was built and in order to get it to function you have to get a rebuilt libcurl.

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Couldn’t Resolve Proxy Couldn’t Resolve Proxy

CURL error code 5 – CURLE_COULDNT_RESOLVE_PROXY (5)

Couldn’t resolve proxy. The given proxy host could not be resolved.

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Couldn’t resolve host Couldn’t resolve host

CURL error code 6 – CURLE_COULDNT_RESOLVE_HOST (6)

Couldn’t resolve host. The given remote host was not resolved.

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Couldn’t connect Couldn’t connect

CURL error code 7 – CURLE_COULDNT_CONNECT (7)

Failed to connect() to host or proxy.

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Weird server reply Weird server reply

CURL error code 8 – CURLE_WEIRD_SERVER_REPLY (8)

The server sent data libcurl couldn’t parse. This error code was known as as CURLE_FTP_WEIRD_SERVER_REPLY before 7.51.0.

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Remote access denied Remote access denied

CURL error code 9 – CURLE_REMOTE_ACCESS_DENIED (9)

We were denied access to the resource given in the URL. For FTP, this occurs while trying to change to the remote directory.

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FTP accept failed FTP accept failed

CURL error code 10 – CURLE_FTP_ACCEPT_FAILED (10)

While waiting for the server to connect back when an active FTP session is used, an error code was sent over the control connection or similar.

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FTP weird pass reply FTP weird pass reply

CURL error code 11 – CURLE_FTP_WEIRD_PASS_REPLY (11)

After having sent the FTP password to the server, libcurl expects a proper reply. This error code indicates that an unexpected code was returned.

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FTP accept timeout FTP accept timeout

CURL error code 12 – CURLE_FTP_ACCEPT_TIMEOUT (12)

During an active FTP session while waiting for the server to connect, the CURLOPT_ACCEPTTIMEOUT_MS (or the internal default) timeout expired.

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FTP weird pasv reply FTP weird pasv reply

CURL error code 13 – CURLE_FTP_WEIRD_PASV_REPLY (13)

libcurl failed to get a sensible result back from the server as a response to either a PASV or a EPSV command. The server is flawed.

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FTP weird 227 format FTP weird 227 format

CURL error code 14 – CURLE_FTP_WEIRD_227_FORMAT (14)

FTP servers return a 227-line as a response to a PASV command. If libcurl fails to parse that line, this return code is passed back.

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FTP cant get host FTP cant get host

CURL error code 15 – CURLE_FTP_CANT_GET_HOST (15)

An internal failure to lookup the host used for the new connection.

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HTTP2 HTTP2

CURL error code 16 – CURLE_HTTP2 (16)

A problem was detected in the HTTP2 framing layer. This is somewhat generic and can be one out of several problems, see the error buffer for details.

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FTP couldnt set type FTP couldnt set type

CURL error code 17 – CURLE_FTP_COULDNT_SET_TYPE (17)

Received an error when trying to set the transfer mode to binary or ASCII.

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Partial file Partial file

CURL error code 18 – CURLE_PARTIAL_FILE (18)

A file transfer was shorter or larger than expected. This happens when the server first reports an expected transfer size, and then delivers data that doesn’t match the previously given size.

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FTP couldnt retr file FTP couldnt retr file

CURL error code 19 – CURLE_FTP_COULDNT_RETR_FILE (19)

This was either a weird reply to a ‘RETR’ command or a zero byte transfer complete.

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Quote error Quote error

CURL error code 21 – CURLE_QUOTE_ERROR (21)

When sending custom “QUOTE” commands to the remote server, one of the commands returned an error code that was 400 or higher (for FTP) or otherwise indicated unsuccessful completion of the command.

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HTTP returned error HTTP returned error

CURL error code 22 – CURLE_HTTP_RETURNED_ERROR (22)

This is returned if CURLOPT_FAILONERROR is set TRUE and the HTTP server returns an error code that is >= 400.

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Write error Write error

CURL error code 23 – CURLE_WRITE_ERROR (23)

An error occurred when writing received data to a local file, or an error was returned to libcurl from a write callback.

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Upload failed Upload failed

CURL error code 25 – CURLE_UPLOAD_FAILED (25)

Failed starting the upload. For FTP, the server typically denied the STOR command. The error buffer usually contains the server’s explanation for this.

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Read error Read error

CURL error code 26 – CURLE_READ_ERROR (26)

There was a problem reading a local file or an error returned by the read callback.

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Out of memory Out of memory

CURL error code 27 – CURLE_OUT_OF_MEMORY (27)

A memory allocation request failed. This is serious badness and things are severely screwed up if this ever occurs.

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Operation timedout Operation timedout

CURL error code 28 – CURLE_OPERATION_TIMEDOUT (28)

Operation timeout. The specified time-out period was reached according to the conditions.

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FTP port failed FTP port failed

CURL error code 30 – CURLE_FTP_PORT_FAILED (30)

The FTP PORT command returned error. This mostly happens when you haven’t specified a good enough address for libcurl to use. See CURLOPT_FTPPORT.

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FTP couldnt use rest FTP couldnt use rest

CURL error code 31 – CURLE_FTP_COULDNT_USE_REST (31)

The FTP REST command returned error. This should never happen if the server is sane.

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Range error Range error

CURL error code 33 – CURLE_RANGE_ERROR (33)

The server does not support or accept range requests.

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HTTP post error HTTP post error

CURL error code 34 – CURLE_HTTP_POST_ERROR (34)

This is an odd error that mainly occurs due to internal confusion.

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SSL connect error SSL connect error

CURL error code 35 – CURLE_SSL_CONNECT_ERROR (35)

A problem occurred somewhere in the SSL/TLS handshake. You really want the error buffer and read the message there as it pinpoints the problem slightly more. Could be certificates (file formats, paths, permissions), passwords, and others.

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Bad download resume Bad download resume

CURL error code 36 – CURLE_BAD_DOWNLOAD_RESUME (36)

The download could not be resumed because the specified offset was out of the file boundary.

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File couldnt read file File couldnt read file

CURL error code 37 – CURLE_FILE_COULDNT_READ_FILE (37)

A file given with FILE:// couldn’t be opened. Most likely because the file path doesn’t identify an existing file. Did you check file permissions?

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LDAP cannot bind LDAP cannot bind

CURL error code 38 – CURLE_LDAP_CANNOT_BIND (38)

LDAP cannot bind. LDAP bind operation failed.

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LDAP search failed LDAP search failed

CURL error code 39 – CURLE_LDAP_SEARCH_FAILED (39)

LDAP search failed.

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Function not found Function not found

CURL error code 41 – CURLE_FUNCTION_NOT_FOUND (41)

Function not found. A required zlib function was not found.

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Aborted by callback Aborted by callback

CURL error code 42 – CURLE_ABORTED_BY_CALLBACK (42)

Aborted by callback. A callback returned “abort” to libcurl.

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Bad function argument Bad function argument

CURL error code 43 – CURLE_BAD_FUNCTION_ARGUMENT (43)

A function was called with a bad parameter.

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Interface failed Interface failed

CURL error code 45 – CURLE_INTERFACE_FAILED (45)

Interface error. A specified outgoing interface could not be used. Set which interface to use for outgoing connections’ source IP address with CURLOPT_INTERFACE.

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Too many redirects Too many redirects

CURL error code 47 – CURLE_TOO_MANY_REDIRECTS (47)

Too many redirects. When following redirects, libcurl hit the maximum amount. Set your limit with CURLOPT_MAXREDIRS.

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Unknown option Unknown option

CURL error code 48 – CURLE_UNKNOWN_OPTION (48)

An option passed to libcurl is not recognized/known. Refer to the appropriate documentation. This is most likely a problem in the program that uses libcurl. The error buffer might contain more specific information about which exact option it concerns.

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Telnet option syntax Telnet option syntax

CURL error code 49 – CURLE_TELNET_OPTION_SYNTAX (49)

A telnet option string was Illegally formatted.

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Got nothing Got nothing

CURL error code 52 – CURLE_GOT_NOTHING (52)

Nothing was returned from the server, and under the circumstances, getting nothing is considered an error.

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SSL engine notfound SSL engine notfound

CURL error code 53 – CURLE_SSL_ENGINE_NOTFOUND (53)

The specified crypto engine wasn’t found.

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SSL engine setfailed SSL engine setfailed

CURL error code 54 – CURLE_SSL_ENGINE_SETFAILED (54)

Failed setting the selected SSL crypto engine as default!

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Send error Send error

CURL error code 55 – CURLE_SEND_ERROR (55)

Failed sending network data.

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Recv error Recv error

CURL error code 56 – CURLE_RECV_ERROR (56)

Failure with receiving network data.

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SSL certproblem SSL certproblem

CURL error code 58 – CURLE_SSL_CERTPROBLEM (58)

problem with the local client certificate.

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SSL cipher SSL cipher

CURL error code 59 – CURLE_SSL_CIPHER (59)

Couldn’t use specified cipher.

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PEER failed verification PEER failed verification

CURL error code 60 – CURLE_PEER_FAILED_VERIFICATION (60)

The remote server’s SSL certificate or SSH md5 fingerprint was deemed not OK. This error code has been unified with ## CURL error code – CURLE_SSL_CACERT since 7.62.0. Its previous value was 51.

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Bad content encoding Bad content encoding

CURL error code 61 – CURLE_BAD_CONTENT_ENCODING (61)

Unrecognized transfer encoding.

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LDAP invalid url LDAP invalid url

CURL error code 62 – CURLE_LDAP_INVALID_URL (62)

Invalid LDAP URL.

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Filesize exceeded Filesize exceeded

CURL error code 63 – CURLE_FILESIZE_EXCEEDED (63)

Maximum file size exceeded.

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Use ssl failed Use ssl failed

CURL error code 64 – CURLE_USE_SSL_FAILED (64)

Requested FTP SSL level failed.

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Send fail rewind Send fail rewind

CURL error code 65 – CURLE_SEND_FAIL_REWIND (65)

When doing a send operation curl had to rewind the data to retransmit, but the rewinding operation failed.

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SSL engine initfailed SSL engine initfailed

CURL error code 66 – CURLE_SSL_ENGINE_INITFAILED (66)

Initiating the SSL Engine failed.

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Login denied Login denied

CURL error code 67 – CURLE_LOGIN_DENIED (67)

The remote server denied curl to login (Added in 7.13.1)

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TFTP notfound TFTP notfound

CURL error code 68 – CURLE_TFTP_NOTFOUND (68)

File not found on TFTP server.

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TFTP perm TFTP perm

CURL error code 69 – CURLE_TFTP_PERM (69)

Permission problem on TFTP server.

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Remote disk full Remote disk full

CURL error code 70 – CURLE_REMOTE_DISK_FULL (70)

Out of disk space on the server.

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TFTP illegal TFTP illegal

CURL error code 71 – CURLE_TFTP_ILLEGAL (71)

Illegal TFTP operation.

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TFTP unknownid TFTP unknownid

CURL error code 72 – CURLE_TFTP_UNKNOWNID (72)

Unknown TFTP transfer ID.

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Remote file exists Remote file exists

CURL error code 73 – CURLE_REMOTE_FILE_EXISTS (73)

File already exists and will not be overwritten.

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TFTP nosuchuser TFTP nosuchuser

CURL error code 74 – CURLE_TFTP_NOSUCHUSER (74)

This error should never be returned by a properly functioning TFTP server.

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Conv failed Conv failed

CURL error code 75 – CURLE_CONV_FAILED (75)

Character conversion failed.

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Conv reqd Conv reqd

CURL error code 76 – CURLE_CONV_REQD (76)

Caller must register conversion callbacks.

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SSL cacert badfile SSL cacert badfile

CURL error code 77 – CURLE_SSL_CACERT_BADFILE (77)

Problem with reading the SSL CA cert (path? access rights?)

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Remote file not found Remote file not found

CURL error code 78 – CURLE_REMOTE_FILE_NOT_FOUND (78)

The resource referenced in the URL does not exist.

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SSH SSH

CURL error code 79 – CURLE_SSH (79)

An unspecified error occurred during the SSH session.

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SSL shutdown failed SSL shutdown failed

CURL error code 80 – CURLE_SSL_SHUTDOWN_FAILED (80)

Failed to shut down the SSL connection.

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Again Again

CURL error code 81 – CURLE_AGAIN (81)

Socket is not ready for send/recv wait till it’s ready and try again. This return code is only returned from curl_easy_recv and curl_easy_send (Added in 7.18.2)

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SSL crl badfile SSL crl badfile

CURL error code 82 – CURLE_SSL_CRL_BADFILE (82)

Failed to load CRL file (Added in 7.19.0)

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SSL issuer error SSL issuer error

CURL error code 83 – CURLE_SSL_ISSUER_ERROR (83)

Issuer check failed (Added in 7.19.0)

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FTP pret failed FTP pret failed

CURL error code 84 – CURLE_FTP_PRET_FAILED (84)

The FTP server does not understand the PRET command at all or does not support the given argument. Be careful when using CURLOPT_CUSTOMREQUEST, a custom LIST command will be sent with PRET CMD before PASV as well. (Added in 7.20.0)

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RTSP cseq error RTSP cseq error

CURL error code 85 – CURLE_RTSP_CSEQ_ERROR (85)

Mismatch of RTSP CSeq numbers.

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RTSP session error RTSP session error

CURL error code 86 – CURLE_RTSP_SESSION_ERROR (86)

Mismatch of RTSP Session Identifiers.

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FTP bad file list FTP bad file list

CURL error code 87 – CURLE_FTP_BAD_FILE_LIST (87)

Unable to parse FTP file list (during FTP wildcard downloading).

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Chunk failed Chunk failed

CURL error code 88 – CURLE_CHUNK_FAILED (88)

Chunk callback reported error.

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No connection available No connection available

CURL error code 89 – CURLE_NO_CONNECTION_AVAILABLE (89)

(For internal use only, will never be returned by libcurl) No connection available, the session will be queued. (added in 7.30.0)

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SSL pinnedpubkeynotmatch SSL pinnedpubkeynotmatch

CURL error code 90 – CURLE_SSL_PINNEDPUBKEYNOTMATCH (90)

Failed to match the pinned key specified with CURLOPT_PINNEDPUBLICKEY.

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SSL invalidcertstatus SSL invalidcertstatus

CURL error code 91 – CURLE_SSL_INVALIDCERTSTATUS (91)

Status returned failure when asked with CURLOPT_SSL_VERIFYSTATUS.

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HTTP2 stream HTTP2 stream

CURL error code 92 – CURLE_HTTP2_STREAM (92)

Stream error in the HTTP/2 framing layer.

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Recursive api call Recursive api call

CURL error code 93 – CURLE_RECURSIVE_API_CALL (93)

An API function was called from inside a callback.

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Auth error Auth error

CURL error code 94 – CURLE_AUTH_ERROR (94)

An authentication function returned an error.

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HTTP3 HTTP3

CURL error code 95 – CURLE_HTTP3 (95)

A problem was detected in the HTTP/3 layer. This is somewhat generic and can be one out of several problems, see the error buffer for details.

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Quic connect error Quic connect error

CURL error code 96 – CURLE_QUIC_CONNECT_ERROR (96)

QUIC connection error. This error may be caused by an SSL library error. QUIC is the protocol used for HTTP/3 transfers.

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Obsolete* Obsolete*

CURL error code * – CURLE_OBSOLETE*

These error codes will never be returned. They were used in an old libcurl version and are currently unused.

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