---
name: "CURLOPT_PROXY_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_PROXY_SSLKEY"
---

# CURLOPT\_PROXY\_SSLKEY(3)

private key file for HTTPS proxy client cert

## NAME

CURLOPT\_PROXY\_SSLKEY - private key file for HTTPS proxy client cert

## SYNOPSIS

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

## DESCRIPTION

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

## 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_PROXY, "https://proxy");
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLCERT, "client.pem");
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLKEY, "key.pem");
    curl_easy_setopt(curl, CURLOPT_PROXY_KEYPASSWD, "s3cret");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in 7.52.0

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\_PROXY\_SSLCERT**(3)](/CURLOPT_PROXY_SSLCERT/3.md), [**CURLOPT\_PROXY\_SSLKEYTYPE**(3)](/CURLOPT_PROXY_SSLKEYTYPE/3.md), [**CURLOPT\_SSLCERT**(3)](/CURLOPT_SSLCERT/3.md), [**CURLOPT\_SSLKEY**(3)](/CURLOPT_SSLKEY/3.md), [**CURLOPT\_SSLKEYTYPE**(3)](/CURLOPT_SSLKEYTYPE/3.md)