---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_SSLKEY
Section: 3
Source: libcurl
See-also:
  - CURLOPT_SSLCERT (3)
  - CURLOPT_SSLKEYTYPE (3)
  - CURLOPT_SSLKEY_BLOB (3)
Protocol:
  - TLS
TLS-backend:
  - OpenSSL
  - mbedTLS
  - Schannel
  - wolfSSL
Added-in: 7.9.3
---

# NAME

CURLOPT_SSLKEY - private key file for TLS and SSL client cert

# SYNOPSIS

~~~c
#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).

(Windows, iOS and macOS) 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.

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%

# EXAMPLE

~~~c
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%

# 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.