CURLOPT_CAINFO - path to Certificate Authority (CA) bundle

Added in curl 7.4.2

Built-in system specific. When curl is built with Secure Transport or Schannel, this option is not set by default.

Pass a char pointer to a null-terminated string naming a file holding one or more certificates to verify the peer with. If CURLOPT_SSL_VERIFYPEER(3) is zero and you avoid verifying the server's certificate, CURLOPT_CAINFO(3) need not even indicate an accessible file. This option is by default set to the system path where libcurl's CA certificate bundle is assumed to be stored, as established at build time. (iOS and macOS) When curl uses Secure Transport this option is supported. If the option is not set, then curl uses the certificates in the system and user Keychain to verify the peer. (Schannel) This option is supported for Schannel in Windows 7 or later but we recommend not using it until Windows 8 since it works better starting then. If the option is not set, then curl uses the certificates in the Windows' store of root certificates (the default for Schannel). 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. The default value for this can be figured out with CURLINFO_CAINFO(3).

int main(void) { CURL *curl = curl_easy_init(); if(curl) { curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/"); curl_easy_setopt(curl, CURLOPT_CAINFO, "/etc/certs/cabundle.pem"); curl_easy_perform(curl); curl_easy_cleanup(curl); } }

Schannel support added in libcurl 7.60.

CURLOPT_CAINFO - path to Certificate Authority (CA) bundle

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. All TLS backends support this option.

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).

CURLINFO_CAINFO(3), CURLOPT_CAINFO_BLOB(3), CURLOPT_CAPATH(3), CURLOPT_CA_CACHE_TIMEOUT(3), CURLOPT_SSL_VERIFYHOST(3), CURLOPT_SSL_VERIFYPEER(3) libcurl 2025-06-16 CURLOPT_CAINFO(3)

#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CAINFO, char *path);