---
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
  - Rustls
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) This option is ignored by the Schannel SSL backend because it
expects 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

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
libcurl-errors(3).
