---
name: "CURLOPT_DEFAULT_PROTOCOL"
section: "3"
platform: "macos"
package: "curl"
version: "166.0.0.0.1"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_DEFAULT_PROTOCOL"
---

# CURLOPT\_DEFAULT\_PROTOCOL(3)

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

## 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)](/curl_easy_perform/3.md)* or *[curl\_multi\_perform(3)](/curl_multi_perform/3.md)* is called. The protocol set supported by libcurl vary depending on how it was built. Use *[curl\_version\_info(3)](/curl_version_info/3.md)* 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)](/CURLOPT_URL/3.md)* for details.

The application does not have to keep the string around after setting this option.

## DEFAULT

NULL (make a guess based on the host)

## PROTOCOLS

All

## 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 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_PROTOCOL/3.md), [**CURLINFO\_SCHEME**(3)](/CURLINFO_SCHEME/3.md), [**CURLOPT\_URL**(3)](/CURLOPT_URL/3.md)