CURLOPT_PROTOCOLS_STR(3) Library Functions Manual CURLOPT_PROTOCOLS_STR(3)
NAME
CURLOPT_PROTOCOLS_STR - allowed protocols
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROTOCOLS_STR, char *spec);
DESCRIPTION
Pass a pointer to a string that holds a comma-separated list of case in-
sensitive protocol names (URL schemes) to allow in the transfer. This
option allows applications to use libcurl built to support a wide range
of protocols but still limit specific transfers to only be allowed to
use a subset of them. By default, libcurl accepts all protocols it was
built with support for. See also CURLOPT_REDIR_PROTOCOLS_STR(3).
If trying to set a non-existing protocol or if no matching protocol at
all is set, it returns error.
These are the available protocols:
DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP,
LDAPS, MQTT, POP3, POP3S, RTMP, RTMPE, RTMPS, RTMPT, RTMPTE, RTMPTS,
RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS, WSS
You can set "ALL" as a short-cut to enable all protocols. Note that by
setting all, you may enable protocols that were not supported the day
you write this but are introduced in a future libcurl version.
curl_version_info(3) can be used to get a list of all supported proto-
cols in the current libcurl. CURLINFO_SCHEME(3) is the recommended way
to figure out the protocol used in a previous transfer.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to restore to the internal default.
DEFAULT
All protocols built-in
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(int argc, char **argv)
{
CURL *curl = curl_easy_init();
if(curl) {
/* pass in the URL from an external source */
curl_easy_setopt(curl, CURLOPT_URL, argv[1]);
/* only allow HTTP, TFTP and SFTP */
curl_easy_setopt(curl, CURLOPT_PROTOCOLS_STR, "http,tftp,sftp");
/* Perform the request */
curl_easy_perform(curl);
}
}
AVAILABILITY
Added in curl 7.85.0
RETURN VALUE
Returns CURLE_UNKNOWN_OPTION if the option is not implemented, CURLE_UN-
SUPPORTED_PROTOCOL if a listed protocol is not supported or disabled,
CURLE_BAD_FUNCTION_ARGUMENT if no protocol is listed else CURLE_OK.
SEE ALSO
CURLINFO_SCHEME(3), CURLOPT_DEFAULT_PROTOCOL(3), CURLOPT_REDIR_PROTO-
COLS_STR(3), CURLOPT_URL(3), curl_version_info(3)
libcurl 2026-07-12 CURLOPT_PROTOCOLS_STR(3)
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