CURLOPT_SSLENGINE(3) Library Functions Manual CURLOPT_SSLENGINE(3)
NAME
CURLOPT_SSLENGINE - Set SSL engine or provider
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLENGINE, char *id);
DESCRIPTION
Pass a pointer to a null-terminated string as parameter. It is used as
the identifier for the engine or provider you want to use for your
private key. OpenSSL 1 had engines, OpenSSL 3 has providers.
The application does not have to keep the string around after setting
this option.
When asking libcurl to use a provider, the application can also
optionally provide a property, a set of name value pairs. Such a
property can be specified separated from the name with a colon (:).
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
PROTOCOLS
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
This option works only with the following TLS backends: OpenSSL
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode result;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_SSLENGINE, "dynamic");
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
AVAILABILITY
Added in curl 7.9.3
RETURN VALUE
CURLE_OK - Engine found.
CURLE_SSL_ENGINE_NOTFOUND - Engine not found, or OpenSSL was not built
with engine support.
CURLE_SSL_ENGINE_INITFAILED - Engine found but initialization failed.
CURLE_NOT_BUILT_IN - Option not built in, OpenSSL is not the SSL
backend.
CURLE_UNKNOWN_OPTION - Option not recognized.
CURLE_OUT_OF_MEMORY - Insufficient heap space.
SEE ALSO
CURLINFO_SSL_ENGINES(3), CURLOPT_SSLENGINE_DEFAULT(3),
CURLOPT_SSLKEY(3)
libcurl 2026-03-23 CURLOPT_SSLENGINE(3)
curl 8.19.0 - Generated Tue Mar 31 13:47:48 CDT 2026