---
name: "CURLOPT_SSLVERSION"
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_SSLVERSION"
---

# CURLOPT\_SSLVERSION(3)

preferred TLS/SSL version

## NAME

CURLOPT\_SSLVERSION - preferred TLS/SSL version

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLVERSION, long version);
```

## DESCRIPTION

Pass a long as parameter to control which version range of SSL/TLS versions to use.

The SSL and TLS versions have typically developed from the most insecure version to be more and more secure in this order through history: SSLv2, SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 and the most recent TLSv1.3.

Use one of the available defines for this purpose. The available options are:

- CURL\_SSLVERSION\_DEFAULT

  The default acceptable version range. The minimum acceptable version is by default TLSv1.2 since 8.16.0 (unless the TLS library has a stricter rule).

- CURL\_SSLVERSION\_TLSv1

  TLSv1.0 or later

- CURL\_SSLVERSION\_SSLv2

  SSLv2 - refused

- CURL\_SSLVERSION\_SSLv3

  SSLv3 - refused

- CURL\_SSLVERSION\_TLSv1\_0

  TLSv1.0 or later

- CURL\_SSLVERSION\_TLSv1\_1

  TLSv1.1 or later

- CURL\_SSLVERSION\_TLSv1\_2

  TLSv1.2 or later

- CURL\_SSLVERSION\_TLSv1\_3

  TLSv1.3 or later

The maximum TLS version can be set by using *one* of the CURL\_SSLVERSION\_MAX\_ macros below. It is also possible to OR *one* of the CURL\_SSLVERSION\_ macros with *one* of the CURL\_SSLVERSION\_MAX\_ macros.

- CURL\_SSLVERSION\_MAX\_DEFAULT

  The flag defines the maximum supported TLS version by libcurl, or the default value from the SSL library is used. libcurl uses a sensible default maximum, which was TLSv1.2 up to before 7.61.0 and is TLSv1.3 since then - assuming the TLS library support it.

- CURL\_SSLVERSION\_MAX\_TLSv1\_0

  The flag defines maximum supported TLS version as TLSv1.0.

- CURL\_SSLVERSION\_MAX\_TLSv1\_1

  The flag defines maximum supported TLS version as TLSv1.1.

- CURL\_SSLVERSION\_MAX\_TLSv1\_2

  The flag defines maximum supported TLS version as TLSv1.2.

- CURL\_SSLVERSION\_MAX\_TLSv1\_3

  The flag defines maximum supported TLS version as TLSv1.3.

## DEFAULT

CURL\_SSLVERSION\_DEFAULT

## PROTOCOLS

This functionality affects  all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

All TLS backends support this option.

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    /* ask libcurl to use TLS version 1.0 or later */
    curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);
    /* Perform the request */
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## HISTORY

SSLv2 is disabled by default since 7.18.1. Other SSL versions availability may vary depending on which backend libcurl has been built to use.

SSLv3 is disabled by default since 7.39.0.

SSLv2 and SSLv3 are refused completely since curl 7.77.0

Since 8.10.0 wolfSSL is fully supported. Before 8.10.0 the MAX macros were not supported with wolfSSL and the other macros did not set a minimum, but restricted the TLS version to only the specified one.

Rustls support added in 8.10.0.

**CURL\_SSLVERSION\_**\* macros became *long* types in 8.16.0, prior to this version a *long* cast was necessary when passed to *[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)*.

## AVAILABILITY

Added in curl 7.1

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_HTTP\_VERSION**(3)](/CURLOPT_HTTP_VERSION/3.md), [**CURLOPT\_IPRESOLVE**(3)](/CURLOPT_IPRESOLVE/3.md), [**CURLOPT\_PROXY\_SSLVERSION**(3)](/CURLOPT_PROXY_SSLVERSION/3.md), [**CURLOPT\_USE\_SSL**(3)](/CURLOPT_USE_SSL/3.md)