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.
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 2026-03-23 CURLOPT_CERTINFO(3)
curl 8.19.0 - Generated Thu Mar 26 18:33:53 CDT 2026