CURLOPT_CERTINFO(3)        Library Functions Manual        CURLOPT_CERTINFO(3)

NAME
       CURLOPT_CERTINFO - request SSL certificate information

SYNOPSIS
       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CERTINFO, long certinfo);

DESCRIPTION
       Pass a long set to 1 to enable libcurl's certificate chain info
       gatherer. With this enabled, libcurl extracts lots of information and
       data about the certificates in the certificate chain used in the SSL
       connection. This data may then be retrieved after a transfer using
       curl_easy_getinfo(3) and its option CURLINFO_CERTINFO(3).

DEFAULT
       0

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

       This option works only with the following TLS backends: GnuTLS,
       OpenSSL, Rustls and Schannel

EXAMPLE
       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLcode result;
           curl_easy_setopt(curl, CURLOPT_URL, "https://www.example.com/");

           /* connect to any HTTPS site, trusted or not */
           curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
           curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);

           curl_easy_setopt(curl, CURLOPT_CERTINFO, 1L);

           result = curl_easy_perform(curl);

           if(result == CURLE_OK) {
             struct curl_certinfo *ci;
             result = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci);

             if(result == CURLE_OK) {
               int i;
               printf("%d certs!\n", ci->num_of_certs);

               for(i = 0; i < ci->num_of_certs; i++) {
                 struct curl_slist *slist;

                 for(slist = ci->certinfo[i]; slist; slist = slist->next)
                   printf("%s\n", slist->data);
               }
             }
           }
           curl_easy_cleanup(curl);
         }
       }

HISTORY
       Schannel support added in 7.50.0. mbedTLS support added in 8.9.0.

AVAILABILITY
       Added in curl 7.19.1

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
       CURLINFO_CAINFO(3), CURLINFO_CAPATH(3), CURLINFO_CERTINFO(3),
       CURLOPT_CAINFO(3), CURLOPT_SSL_VERIFYPEER(3)

libcurl                           2026-09-02               CURLOPT_CERTINFO(3)