---
name: "CURLOPT_SSL_EC_CURVES"
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_SSL_EC_CURVES"
---

# CURLOPT\_SSL\_EC\_CURVES(3)

key exchange curves

## NAME

CURLOPT\_SSL\_EC\_CURVES - key exchange curves

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_EC_CURVES, char *alg_list);
```

## DESCRIPTION

Pass a string as parameter with a colon delimited list of (EC) algorithms. This option defines the client's key exchange algorithms in the SSL handshake (if the SSL backend libcurl is built to use supports it).

## DEFAULT

"", embedded in SSL backend

## PROTOCOLS

HTTP

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_SSL_EC_CURVES, "X25519:P-521");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in 7.73.0. Supported by the OpenSSL backend.

## RETURN VALUE

Returns CURLE\_OK if the option is supported, and CURLE\_UNKNOWN\_OPTION if not.

## SEE ALSO

[**CURLOPT\_SSL\_CIPHER\_LIST**(3)](/CURLOPT_SSL_CIPHER_LIST/3.md), [**CURLOPT\_SSL\_OPTIONS**(3)](/CURLOPT_SSL_OPTIONS/3.md), [**CURLOPT\_TLS13\_CIPHERS**(3)](/CURLOPT_TLS13_CIPHERS/3.md)