1---
2c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
3SPDX-License-Identifier: curl
4Title: CURLOPT_SSL_ENABLE_ALPN
5Section: 3
6Source: libcurl
7See-also:
8  - CURLOPT_SSL_ENABLE_NPN (3)
9  - CURLOPT_SSL_OPTIONS (3)
10---
11
12# NAME
13
14CURLOPT_SSL_ENABLE_ALPN - Application Layer Protocol Negotiation
15
16# SYNOPSIS
17
18~~~c
19#include <curl/curl.h>
20
21CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_ALPN, long npn);
22~~~
23
24# DESCRIPTION
25
26Pass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. This
27option enables/disables ALPN in the SSL handshake (if the SSL backend libcurl
28is built to use supports it), which can be used to negotiate http2.
29
30# DEFAULT
31
321, enabled
33
34# PROTOCOLS
35
36HTTP
37
38# EXAMPLE
39
40~~~c
41int main(void)
42{
43  CURL *curl = curl_easy_init();
44  if(curl) {
45    CURLcode res;
46    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
47    curl_easy_setopt(curl, CURLOPT_SSL_ENABLE_ALPN, 0L);
48    res = curl_easy_perform(curl);
49    curl_easy_cleanup(curl);
50  }
51}
52~~~
53
54# AVAILABILITY
55
56Added in 7.36.0
57
58# RETURN VALUE
59
60Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
61