CURLOPT_IPRESOLVE(3)

okay bestie, welcome to the CURLOPT_IPRESOLVE(3) page from the Library Functions Manual — we're talking about picking which IP protocol version to use, and it's honestly iconic 💅

🎀 NAME 🎀

CURLOPT_IPRESOLVE — the IP protocol version to use ✨

🦋 SYNOPSIS 🦋

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IPRESOLVE, long resolve);

🌸 DESCRIPTION 🌸

This one lets an application choose what kind of IP addresses to use when it's establishing a connection or choosing one from the connection pool. It's super interesting when you're using hostnames that resolve to more than one IP family — like, okay, which one are we actually picking? 👀

quick heads-up: 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. no cap.

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 🦋

💅 DEFAULT 💅

CURL_IPRESOLVE_WHATEVER — periodt.

🌈 PROTOCOLS 🌈

This functionality affects all supported protocols ⭐

🍓 EXAMPLE 🍓

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    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, CURL_IPRESOLVE_V6);

    result = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
  }
}

🧚 HISTORY 🧚

The CURL_IPRESOLVE_* macros became long types in 8.15.0; before this version a long cast was necessary when passed to curl_easy_setopt(3) ⏳

👑 AVAILABILITY 👑

Added in curl 7.10.8 ✨

🔥 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 💜

• CURLOPT_HTTP_VERSION(3)
• CURLOPT_RESOLVE(3)
• CURLOPT_SSLVERSION(3)

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bye bestie 🫶 this page is from libcurl, dated 2026-10-12 — and yes, the footer vibe is immaculate 💖