CURLOPT_CERTINFO(3) - Man pages

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 gath-
       erer. With this enabled, libcurl extracts lots of information  and  data
       about  the certificates in the certificate chain used in the SSL connec-
       tion.  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.

       This option works only with the following TLS backends: GnuTLS, OpenSSL,
       Schannel, Secure Transport and rustls

EXAMPLE
       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLcode res;
           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);

           res = curl_easy_perform(curl);

           if(!res) {
             struct curl_certinfo *ci;
             res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci);

             if(!res) {
               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.  Secure  Transport  support  added  in
       7.79.0.  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),   CUR-
       LOPT_CAINFO(3), CURLOPT_SSL_VERIFYPEER(3)

libcurl                            2026-07-12               CURLOPT_CERTINFO(3)

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