CURLOPT\_IPRESOLVE(3) Library Functions Manual CURLOPT\_IPRESOLVE(3)

# [NAME](#NAME)

CURLOPT\_IPRESOLVE - IP protocol version to use

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#DESCRIPTION)

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](#CURL_IPRESOLVE_WHATEVER)

Default, can use addresses of all IP versions that your system allows.

[CURL\_IPRESOLVE\_V4](#CURL_IPRESOLVE_V4)

Uses only IPv4 addresses.

[CURL\_IPRESOLVE\_V6](#CURL_IPRESOLVE_V6)

Uses only IPv6 addresses.

# [DEFAULT](#DEFAULT)

CURL\_IPRESOLVE\_WHATEVER

# [PROTOCOLS](#PROTOCOLS)

This functionality affects all supported protocols

# [EXAMPLE](#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](#HISTORY)

**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)*](/man/os/curl/curl_easy_setopt.3).

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.10.8

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/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)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

[**CURLOPT\_HTTP\_VERSION**(3)](/man/os/curl/CURLOPT_HTTP_VERSION.3), [**CURLOPT\_RESOLVE**(3)](/man/os/curl/CURLOPT_RESOLVE.3), [**CURLOPT\_SSLVERSION**(3)](/man/os/curl/CURLOPT_SSLVERSION.3)

2026-10-19 libcurl

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Document: CURLOPT_IPRESOLVE(3) from curl 8.23.0-r1 (Chainguard OS)
Source: https://github.com/curl/curl.git