---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_DEFAULT_PROTOCOL
Section: 3
Source: libcurl
See-also:
  - CURLINFO_PROTOCOL (3)
  - CURLINFO_SCHEME (3)
  - CURLOPT_URL (3)
Protocol:
  - All
Added-in: 7.45.0
---

# NAME

CURLOPT_DEFAULT_PROTOCOL - default protocol to use if the URL is missing a
scheme name

# SYNOPSIS

~~~c
#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%

# EXAMPLE

~~~c
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%

# 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.