CURLOPT_URL(3) Library Functions Manual CURLOPT_URL(3)
NAME
CURLOPT_URL - URL for this transfer
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_URL, char *URL);
DESCRIPTION
Pass in a pointer to the URL to work with. The parameter should be a
char * to a null-terminated string which must be URL-encoded in the fol-
lowing format:
scheme://host:port/path
For a greater explanation of the format please see RFC 3986.
libcurl does not validate the syntax or use the URL until the transfer
is started. Even if you set a crazy value here, curl_easy_setopt(3)
might still return CURLE_OK.
If the given URL is missing a scheme name (such as "http://" or "ftp://"
etc) then libcurl guesses based on the host. If the outermost subdomain
name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP then that protocol gets
used, otherwise HTTP is used. Since 7.45.0 guessing can be disabled by
setting a default protocol, see CURLOPT_DEFAULT_PROTOCOL(3) for details.
Should the protocol, either as specified by the URL scheme or deduced by
libcurl from the hostname, not be supported by libcurl then CURLE_UNSUP-
PORTED_PROTOCOL is returned from either the curl_easy_perform(3) or
curl_multi_perform(3) functions when you call them. Use curl_ver-
sion_info(3) for detailed information of which protocols are supported
by the build of libcurl you are using.
CURLOPT_PROTOCOLS_STR(3) can be used to limit what protocols libcurl may
use for this transfer, independent of what libcurl has been compiled to
support. That may be useful if you accept the URL from an external
source and want to limit the accessibility.
The CURLOPT_URL(3) string is ignored if CURLOPT_CURLU(3) is set.
Either CURLOPT_URL(3) or CURLOPT_CURLU(3) must be set before a transfer
is started.
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. Note however
that libcurl needs a URL set to be able to performed a transfer.
The parser used for handling the URL set with CURLOPT_URL(3) is the same
that curl_url_set(3) uses.
ENCODING
The string pointed to in the CURLOPT_URL(3) argument is generally ex-
pected to be a sequence of characters using an ASCII compatible encod-
ing.
If libcurl is built with IDN support, the server name part of the URL
can use an "international name" by using the current encoding (according
to locale) or UTF-8 (when WinIDN is used; or a Windows Unicode build us-
ing libidn2).
If libcurl is built without IDN support, the server name is used exactly
as specified when passed to the name resolver functions.
DEFAULT
NULL. If this option is not set, no transfer can be performed.
SECURITY CONCERNS
Applications may at times find it convenient to allow users to specify
URLs for various purposes and that string would then end up fed to this
option.
Getting a URL from an external untrusted party brings several security
concerns:
If you have an application that runs as or in a server application, get-
ting an unfiltered URL can easily trick your application to access a lo-
cal resource instead of a remote. Protecting yourself against localhost
accesses is hard when accepting user provided URLs.
Such custom URLs can also access other ports than you planned as port
numbers are part of the regular URL format. The combination of a local
host and a custom port number can allow external users to play tricks
with your local services.
Accepting external URLs may also use other protocols than http:// or
other common ones. Restrict what accept with CURLOPT_PROTOCOLS_STR(3).
User provided URLs can also be made to point to sites that redirect fur-
ther on (possibly to other protocols too). Consider your CURLOPT_FOL-
LOWLOCATION(3) and CURLOPT_REDIR_PROTOCOLS_STR(3) settings.
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_perform(curl);
}
}
AVAILABILITY
Added in curl 7.1
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 not parse the given string so given a
bad URL, it is not detected until curl_easy_perform(3) or similar is
called.
SEE ALSO
CURLINFO_REDIRECT_URL(3), CURLOPT_CURLU(3), CURLOPT_FORBID_REUSE(3),
CURLOPT_FRESH_CONNECT(3), CURLOPT_PATH_AS_IS(3), CURLOPT_PROTO-
COLS_STR(3), curl_easy_perform(3), curl_url_get(3), curl_url_set(3)
libcurl 2026-07-12 CURLOPT_URL(3)
Generated by dwww version 1.16 on Sat Oct 3 05:05:59 CEST 2026.