CURLOPT_DEFAULT_PROTOCOL(3) Library Functions Manual
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_PROTOCOL 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) {
CURLcode result;
/* 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 */
result = curl_easy_perform(curl);
curl_easy_cleanup(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 2026-06-09 CURLOPT_DEFAULT_PROTOCOL(3)
curl 8.20.0 - Generated Tue Jun 9 14:41:38 CDT 2026