CURLOPT_IPRESOLVE - IP protocol version to use

Added in curl 7.10.8

CURL_IPRESOLVE_WHATEVER

Allows an application to select what kind of IP addresses to use when establishing a connection or choosing one from the connection pool. This is interesting when using hostnames that resolve to more than one IP family. If the URL provided for a transfer contains a numerical IP version as a host name, this option does not override or prohibit libcurl from using that IP version. Available values for this option are: CURL_IPRESOLVE_WHATEVER Default, can use addresses of all IP versions that your system allows. CURL_IPRESOLVE_V4 Uses only IPv4 addresses. CURL_IPRESOLVE_V6 Uses only IPv6 addresses.

int main(void) { CURL *curl = curl_easy_init(); if(curl) { CURLcode res; curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin"); /* of all addresses example.com resolves to, only IPv6 ones are used */ curl_easy_setopt(curl, CURLOPT_IPRESOLVE, (long)CURL_IPRESOLVE_V6); res = curl_easy_perform(curl); curl_easy_cleanup(curl); } }

CURLOPT_IPRESOLVE - IP protocol version to use

This functionality affects all supported protocols

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).

CURLOPT_HTTP_VERSION(3), CURLOPT_RESOLVE(3), CURLOPT_SSLVERSION(3) libcurl 2025-06-16 CURLOPT_IPRESOLVE(3)

#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IPRESOLVE, long resolve);