---
name: "CURLOPT_PROTOCOLS_STR"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_PROTOCOLS_STR"
---

# CURLOPT\_PROTOCOLS\_STR(3)

allowed protocols

## 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 insensitive 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)](/CURLOPT_REDIR_PROTOCOLS_STR/3.md)*.

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, MQTTS, POP3, POP3S, RTSP, SCP, SFTP, 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)](/curl_version_info/3.md)* can be used to get a list of all supported protocols in the current libcurl. *[CURLINFO\_SCHEME(3)](/CURLINFO_SCHEME/3.md)* 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) {
    CURLcode result;
    /* 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 */
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## HISTORY

RTMP and its related protocol schemes are not supported since curl 8.20.0

SMB and SMBS were removed in curl 8.23.0

## AVAILABILITY

Added in curl 7.85.0

## RETURN VALUE

Returns CURLE\_UNKNOWN\_OPTION if the option is not implemented, CURLE\_UNSUPPORTED\_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)](/CURLINFO_SCHEME/3.md), [**CURLOPT\_DEFAULT\_PROTOCOL**(3)](/CURLOPT_DEFAULT_PROTOCOL/3.md), [**CURLOPT\_REDIR\_PROTOCOLS\_STR**(3)](/CURLOPT_REDIR_PROTOCOLS_STR/3.md), [**CURLOPT\_URL**(3)](/CURLOPT_URL/3.md), [**curl\_version\_info**(3)](/curl_version_info/3.md)