---
name: "CURLOPT_SSL_ENABLE_NPN"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_SSL_ENABLE_NPN"
---

# CURLOPT\_SSL\_ENABLE\_NPN(3)

use NPN

## NAME

CURLOPT\_SSL\_ENABLE\_NPN - use NPN

## SYNOPSIS

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

## DESCRIPTION

Deprecated. Setting this option has no function.

Pass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. This option enables/disables NPN in the SSL handshake (if the SSL backend libcurl is built to use supports it), which can be used to negotiate http2.

## DEFAULT

1, enabled

## PROTOCOLS

This functionality affects  all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

All TLS backends support this option.

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_SSL_ENABLE_NPN, 1L);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## DEPRECATED

Deprecated since 7.86.0

## AVAILABILITY

Added in curl 7.36.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_SSL\_ENABLE\_ALPN**(3)](/CURLOPT_SSL_ENABLE_ALPN/3.md), [**CURLOPT\_SSL\_OPTIONS**(3)](/CURLOPT_SSL_OPTIONS/3.md)