nginx

First check the version with nginx -v. The setting moved in version 1.25.1.

nginx 1.25.1 and newer, in the site's server { … } block for port 443:

server {
    listen 443 ssl;
    http2 on;
    # …
}

Older nginx (for example 1.22 on Debian 12, 1.24 on Ubuntu 24.04), add http2 to the listen line:

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    # …
}

The site's file is in /etc/nginx/sites-available/ on Debian and Ubuntu and in /etc/nginx/conf.d/ on Rocky, Alma and CentOS. Test and apply:

sudo nginx -t && sudo systemctl reload nginx

Apache and LiteSpeed

With server access (Apache). HTTP/2 is mod_http2, available since Apache 2.4.17. On Debian and Ubuntu enable it with sudo a2enmod http2; on Rocky, Alma and CentOS install it with sudo dnf install mod_http2. Then add this to the <VirtualHost *:443> of the site, or once to the main configuration for all sites:

Protocols h2 http/1.1

One condition: HTTP/2 does not work with the prefork MPM, which Debian and Ubuntu use when PHP runs as mod_php. Check with apachectl -V | grep -i mpm. If it says prefork, switch to PHP-FPM and the event MPM first (replace 8.3 with your PHP version):

sudo apt install php8.3-fpm
sudo a2dismod php8.3 mpm_prefork
sudo a2enmod mpm_event proxy_fcgi setenvif http2
sudo a2enconf php8.3-fpm
sudo apachectl configtest && sudo systemctl restart apache2

A change of MPM needs a full restart, not a reload. On Rocky, Alma and CentOS PHP-FPM with event is already the default.

LiteSpeed serves HTTP/2 (and HTTP/3) on HTTPS without any setting. A LiteSpeed host that answers only with HTTP/1.1 has turned it off at the server level; ask support.

cPanel

Shared hosting: HTTP/2 is a server-wide setting that only the host can change. Ask support to turn it on; most hosts already have it.

Your own server with WHM:

1. Open WHM → EasyApache 4 and click Customize next to the current profile.
2. Under Apache MPM, choose mod_mpm_event (or mod_mpm_worker). HTTP/2 does not work with prefork.
3. Under Apache Modules, turn on mod_http2.
4. Go to Review and click Provision.

If the server still runs PHP as an Apache module (DSO), switching away from prefork requires moving PHP to PHP-FPM, which you do in MultiPHP Manager.

Plesk

In Plesk, nginx answers visitors and HTTP/2 is turned on by default in current versions. If the check shows HTTP/1.1, turn it on from the server's command line:

plesk bin http2_pref --enable

HTTP/2 needs nginx: if it was turned off (the site runs on Apache alone), turn it back on with plesk sbin nginxmng --enable or ask the host. On shared Plesk hosting, ask the host to run the command above.

Cloudflare

When the site runs behind Cloudflare (orange cloud), Cloudflare serves visitors over HTTP/2 on every plan, whatever the origin server supports. HTTP/3 can be turned on in the domain's Network settings (HTTP/3 (with QUIC)).

If the check still shows HTTP/1.1, the record is probably DNS only (grey cloud), so visitors talk to your server directly. Turn on the proxy or fix the server using its tab.

Node.js and Next.js

Node.js has an http2 module, but in production a Node or Next.js application usually sits behind nginx, a load balancer or a platform such as Vercel, and that is where HTTP/2 is decided. Vercel and Netlify serve HTTP/2 and HTTP/3 by default. Behind your own nginx, follow the nginx tab; the connection from nginx to the application can stay HTTP/1.1.

IIS and ASP.NET

IIS 10 (Windows Server 2016 and newer) uses HTTP/2 automatically for every HTTPS binding. IIS 8.5 and older (Windows Server 2012 R2) cannot do it; the only way there is a newer Windows Server or a proxy such as Cloudflare in front.

On Windows Server 2019 and newer, the HTTPS binding has a Disable HTTP/2 checkbox (Site → Bindings → Edit). Make sure it is not ticked.