CURLOPT_DEFAULT_PROTOCOL(3) Library Functions ManualCURLOPT_DEFAULT_PROTOCOL(3)
NAME
CURLOPT_DEFAULT_PROTOCOL - default protocol to use if the URL is missing
a scheme name
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DEFAULT_PROTOCOL,
char *protocol);
DESCRIPTION
This option tells libcurl to use protocol if the URL is missing a scheme
name.
Use one of these protocol (scheme) names:
dict, file, ftp, ftps, gopher, http, https, imap, imaps, ldap, ldaps,
pop3, pop3s, rtsp, scp, sftp, smb, smbs, smtp, smtps, telnet, tftp
An unknown or unsupported protocol causes error CURLE_UNSUPPORTED_PROTO-
COL when libcurl parses a URL without a scheme. Parsing happens when
curl_easy_perform(3) or curl_multi_perform(3) is called. The protocol
set supported by libcurl vary depending on how it was built. Use
curl_version_info(3) if you need a list of protocol names supported by
the build of libcurl that you are using.
This option does not change the default proxy protocol (http).
Without this option libcurl would make a guess based on the host, see
CURLOPT_URL(3) for details.
The application does not have to keep the string around after setting
this option.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.
DEFAULT
NULL (make a guess based on the host)
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
/* set a URL without a scheme */
curl_easy_setopt(curl, CURLOPT_URL, "example.com");
/* set the default protocol (scheme) for schemeless URLs */
curl_easy_setopt(curl, CURLOPT_DEFAULT_PROTOCOL, "https");
/* Perform the request */
curl_easy_perform(curl);
}
}
AVAILABILITY
Added in curl 7.45.0
RETURN VALUE
CURLE_OK if the option is supported.
CURLE_OUT_OF_MEMORY if there was insufficient heap space.
CURLE_UNKNOWN_OPTION if the option is not supported.
SEE ALSO
CURLINFO_PROTOCOL(3), CURLINFO_SCHEME(3), CURLOPT_URL(3)
libcurl 2026-07-12 CURLOPT_DEFAULT_PROTOCOL(3)
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