Enable HTTP/2 (was SPDY) on your Apache webserver

The HTTP/1.1 which most webserver use has been around since the start of the web.

Now there's an alternative which most browsers support, HTTP/2 - the protocol formerly known in its infancy as Google SPDY.

Its a binary protocol (not plain text as HTTP/1.1), and is generally more efficient all round for both server and browser.

For example, it solves the multiplexing (getting multiple files in parallel from the same website) problem, so you no longer need to do domain name sharding (i.e. splitting your resources over several domain names - a.example.com, b.example.com, c.example.com) to increase throughput.

Before you begin! Browsers only seem to support HTTP/2 on secure HTTPS websites, so you need to upgrade your website to HTTPS first.

So how do you enable it?

First, enable the Apache HTTP2 module. This is a bit dependent upon your flavour of Unix - you might have to use a2enmod, or more simply, something like

#LoadModule http2_module /usr/lib/apache2/modules/mod_http2.so

Then, add this to the server config (or virtual host)

# set http/2 with http/1.1 as a fallback
Protocols h2 http/1.1

When you've done it, there's a test tool here.