CURLOPT_SSLCERTTYPE(3)

okay bestie, this is CURLOPT_SSLCERTTYPE(3) from the Library Functions Manual — brought to you by libcurl, and it's all about the type of your client SSL certificate. 💅

🎀 NAME 🎀

CURLOPT_SSLCERTTYPE — type of client SSL certificate. Short, sweet, iconic.

🌸 SYNOPSIS 🌸

First you include the header, then you call the function like this:

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLCERTTYPE, char *type);

💖 DESCRIPTION 💖

Okay so: you pass a pointer to a null-terminated string as the parameter, and that string should be the format of your certificate. ✨

Supported formats are "PEM" and "DER", except with Schannel. OpenSSL and Schannel support "P12" for PKCS#12-encoded files. GnuTLS supports P12 starting with curl 8.11.0.

Your application does not have to keep the string around after setting this option — set it, and you're free. 🫶

Using this option multiple times makes the last set string override the previous ones. Set it to NULL and it restores back to the internal default.

💜 DEFAULT 💜

"PEM" — that's the default, no cap.

🦋 PROTOCOLS 🦋

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

This option works only with the following TLS backends: GnuTLS, OpenSSL, Schannel, mbedTLS and wolfSSL.

✨ EXAMPLE ✨

Here's the little main character snippet, exactly as it should be:

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_SSLCERT, "client.pem");
    curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "PEM");
    curl_easy_setopt(curl, CURLOPT_SSLKEY, "key.pem");
    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

🎀 AVAILABILITY 🎀

Added in curl 7.9.3. A classic. 💖

🌈 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).

🫶 SEE ALSO 🫶

• CURLOPT_SSLCERT(3)
• CURLOPT_SSLKEY(3)

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💖 cute sign-off: source/version libcurl, date 2026-10-12, page CURLOPT_SSLCERTTYPE(3) — byeee, go set those cert types bestie 💅✨