---
name: "CURLOPT_SSLKEY"
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_SSLKEY"
---

# CURLOPT\_SSLKEY(3)

private key file for TLS and SSL client cert

## NAME

CURLOPT\_SSLKEY - private key file for TLS and SSL client cert

## SYNOPSIS

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

## DESCRIPTION

Pass a pointer to a null-terminated string as parameter. The string should be the filename of your private key. The default format is "PEM" and can be changed with *[CURLOPT\_SSLKEYTYPE(3)](/CURLOPT_SSLKEYTYPE/3.md)*.

(Windows, iOS and Mac OS X) This option is ignored by Secure Transport and Schannel SSL backends because they expect the private key to be already present in the key-chain or PKCS#12 file containing the certificate.

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

## DEFAULT

NULL

## PROTOCOLS

All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

## 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_SSLCERT, "client.pem");
    curl_easy_setopt(curl, CURLOPT_SSLKEY, "key.pem");
    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

If built TLS enabled.

## RETURN VALUE

Returns CURLE\_OK if TLS is supported, CURLE\_UNKNOWN\_OPTION if not, or CURLE\_OUT\_OF\_MEMORY if there was insufficient heap space.

## SEE ALSO

[**CURLOPT\_SSLCERT**(3)](/CURLOPT_SSLCERT/3.md), [**CURLOPT\_SSLKEYTYPE**(3)](/CURLOPT_SSLKEYTYPE/3.md), [**CURLOPT\_SSLKEY\_BLOB**(3)](/CURLOPT_SSLKEY_BLOB/3.md)