CURLOPT_DOH_URL(3) Library Functions Manual CURLOPT_DOH_URL(3)
NAME
CURLOPT_DOH_URL - provide the DNS-over-HTTPS URL
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_URL, char *URL);
DESCRIPTION
Pass in a pointer to a URL for the DoH server to use for name resolving.
The parameter should be a char pointer to a null-terminated string which
must be a valid and correct HTTPS URL.
libcurl does not validate the syntax or use this variable until the
transfer is issued. Even if you set a crazy value here, curl_easy_se-
topt(3) still returns CURLE_OK.
curl sends POST requests to the given DNS-over-HTTPS URL.
To find the DoH server itself, which might be specified using a name,
libcurl uses the default name lookup function. You can bootstrap that by
providing the address for the DoH server with CURLOPT_RESOLVE(3).
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.
INHERIT OPTIONS
DoH lookups use SSL and some SSL settings from your transfer are inher-
ited, like CURLOPT_SSL_CTX_FUNCTION(3).
The hostname and peer certificate verification settings are not inher-
ited but can be controlled separately via CURLOPT_DOH_SSL_VERIFYHOST(3)
and CURLOPT_DOH_SSL_VERIFYPEER(3).
A set CURLOPT_OPENSOCKETFUNCTION(3) callback is not inherited.
KNOWN BUGS
Even when DoH is set to be used with this option, there are still some
name resolves that are performed without it, using the default name re-
solver mechanism. This includes name resolves done for CURLOPT_INTER-
FACE(3), CURLOPT_FTPPORT(3), a proxy type set to CURLPROXY_SOCKS4 or
CURLPROXY_SOCKS5 and probably some more.
DEFAULT
NULL
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_setopt(curl, CURLOPT_DOH_URL, "https://dns.example.com");
curl_easy_perform(curl);
}
}
AVAILABILITY
Added in curl 7.62.0
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).
Note that curl_easy_setopt(3) does immediately parse the given string so
when given a bad DoH URL, libcurl might not detect the problem until it
later tries to resolve a name with it.
SEE ALSO
CURLOPT_DNS_CACHE_TIMEOUT(3), CURLOPT_RESOLVE(3), CURLOPT_VERBOSE(3)
libcurl 2026-07-12 CURLOPT_DOH_URL(3)
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