Enabling Gzip Encoding

In the Delivery section of Apple's HLS Authoring specification, 10.1 states that "the server MUST deliver playlists using gzip content-encoding."

This article will show you how to enable gzip encoding for the Apache2 and Nginx web servers. The instructions are specifically for the Ubuntu Linux distribution so the location of the files you will need to edit may vary depending on what distribution you are using.

Apache2

To enable gzip compression for HLS playlists, add the following lines to the main Apache configuration file (e.g. /etc/apache2/apache2.conf):

<IfModule mod_deflate.c>
	AddOutputFilterByType DEFLATE  application/vnd.apple.mpegurl

	# Set compression level (1-9, 9 being maximum compression)
	DeflateCompressionLevel 6
</IfModule>

This tells Apache to compress any files with the "application/vnd.apple.mpegurl" MIME type, which just happens to correspond to MIME type of an HLS playlist.

Reload (or restart) Apache to enable the changes.

To test the configuration and confirm gzip compression is working, either use a browser developer tool (e.g. Chrome Dev tools) and check the response headers, or use curl:

$ curl -H "Accept-Encoding: gzip" -I http://yourdomain.com/playlist.m3u8

Look for the "Content-Encoding: gzip" header in the server’s response. If it's present, gzip compression is enabled.

Nginx

To enable compression in Nginx, set the gzip directive to on. By default, Nginx will only compress HTML files (text/html). To compress HLS playlists, you will also need to set the gzip_types directive and set it to the MIME type of an HLS playlist.

Here's an example (default) server configuration that enables gzip compression for HLS playlists:

server {
    listen       80;
    listen  [::]:80;
    server_name  localhost;

    gzip on;
    gzip_types application/vnd.apple.mpegurl;
    gzip_vary on;
    

    location / {
        root   /usr/share/nginx/html;
        index  index.html index.htm;
    }
}

To check that gzip compression is enabled, run the following command, replacing the URL with the URL of your playlist:

$ curl -H "Accept-Encoding: gzip" -I http://yourdomain.com/playlist.m3u8

You should see a response like this:

HTTP/1.1 200 OK
Server: nginx/1.26.2
Date: Wed, 26 Mar 2025 18:22:32 GMT
Content-Type: application/vnd.apple.mpegurl
Connection: keep-alive
Vary: Accept-Encoding
Content-Encoding: gzip

Nginx also has the gzip_min_length directive, which allows you to specify the minimum length (in bytes) of the file to be gzipped; the default is 20 bytes meaning that if your playlists are less than this, they won't be compressed. Why would you want to set this? Well, although the guidelines state that playlists must be compressed, it really depends on the size of your playlist. Nginx compresses the files at runtime so it can add considerable processing overhead, which could negatively affect performance. Something to think about.

The gzip directives that configure compression can be included either in the http context or in a server or location block. The example config above is for a specific site. If you want to apply the configuration globally then you would add the gzip directives to the http context in the file /etc/nginx/nginx.conf.