Brotli Compression: What it is, how it works, and how to activate it

Have you ever wondered how to make a website load faster without changing anything about its appearance? The key lies in how the data is transmitted from the server to the user's browser. This transmission can be optimized using compression algorithms that make files smaller.

Brotli is one of those algorithms, and it's not just any one: It is the new standard that is gaining ground against the veteran GZIP. Although both pursue the same goal - compressing files to reduce size and improve loading times - Brotli does it with better resultsBelow, we'll explain in detail what Brotli is, how it works, why it's becoming a favorite option, and how you can activate it on your website, especially if you use WordPress.

What is Brotli and how does it work?

Brotli is a lossless compression algorithm developed by Google. Its first application was in the compression of web font files, but with There It has been optimized to work with all types of data transmitted over HTTP, including HTML, CSS, JavaScript, and more.

It works by detecting repetitive patterns in the content and replacing them with shorter references.This is achieved through two types of dictionaries:

• Static dictionary: Contains over 13.000 common words in six languages ​​and common elements of HTML, CSS, and JS code. Brotli can detect phrases like type=»text/javascript» or tags like to encode them with shorter references.
• Dynamic dictionary: It is generated in real time by analyzing transmitted data. It works as a sliding window of up to 16 MB, saving recent patterns for immediate reuse when they reappear.

Both dictionaries allow Brotli to compress data with a superior efficiency to GZIP. Additionally, it supports 12 compression levels, from 0 to 11, where 0 is the fastest (but least efficient) and 11 the most comprehensive (although slower and more CPU intensive).

Advantages of Brotli compression over GZIP

The main advantage of Brotli over GZIP is its higher compression ratio., which means that Compressed files are smaller. This translates to:

• Lower bandwidth consumption.
• Improved web performance, especially on mobile devices or slow connections.
• Faster loads and improved Core Web Vitals.

A study by Akamai that analyzed 1000 URLs showed that Brotli can save:

• 21% more in HTML.
• 14% in JavaScript.
• 17% in CSS.

For example, a 418 KB HTML file can be compressed with:

• GZIP level 9: 78,7 KB.
• Brotli level 11: 57,2 KB.

If you set Brotli to level 3, you get a file of 76,5 KB, practically the same as GZIP, but with lower resource consumption.

Brotli compression levels and their impact on performance

As mentioned, Brotli allows you to adjust the compression between 0 and 11. This setting influences:

• the speed of compression and decompression.
• the server's CPU load.
• the final size of the file.

Although the maximum tier offers the best rates, intermediate levels between 4 and 6 They are recommended for their balance between load and performance. In fact, Cloudflare has been using Level 4 since 2017, and in 2023 they announced full support for Level 11 to take full advantage of its potential.

Brotli compatibility with browsers and servers

Brotli is currently compatible with over 95% of browsers available on the market., including Chrome, Firefox, Edge, Safari, Brave, and Opera.

Regarding web servers, compatibility is as follows:

• Apache: supports Brotli since version 2.4 and can be activated by adding AddOutputFilterByType BROTLI_COMPRESS in the File .htaccess.
• Nginx: requires compiling the Brotli module. After installation, it is activated by editing nginx.conf with directives such as brotli on; y brotli_types.
• LiteSpeed: It is fully compatible and comes activated by default on servers with cPanel that use it.

Furthermore, Major CDN providers such as Cloudflare, KeyCDN, CDN77, and Amazon CloudFront have adopted Brotli. In many cases, its use is already enabled by default.

How to tell if your site uses Brotli compression

Want to check if your website is using Brotli? You can check this using several options:

1. Online tools

• KeyCDN Brotli Test: https://tools.keycdn.com/brotli-test
• Gift of Speed: https://www.giftofspeed.com/GZIP-test/
• Paul Calvano Compression Test: https://tools.paulcalvano.com/compression.php

2. HTTP Headers

You can also do it with the terminal using:

curl -LH "Accept-Encoding: br" -I https://tuweb.com

If the answer appears content-encoding: brmeans that your website is using Brotli.

How to activate Brotli in WordPress

In WordPress, enabling Brotli is highly server-dependent.However, some caching plugins offer support for Brotli or allow you to enable GZIP if Brotli is not available.

Helpful Tips:

1. Supported cache plugins

Plugins like W3 Total Cache, WP Rocket or official Cloudflare plugin can support Brotli or enable GZIP as an alternative if your server doesn't support it directly.

2. Check server configuration

Many hosting providers already activate Brotli automatically, such as:

• Kinsta
• SiteGround
• WP Engine
• LucusHost
• Raiola Networks

In most cases, it is already activated and you do not need to do anything additional.. Consult technical support if you have any questions.

Cloudflare and Brotli end-to-end compression

Cloudflare has taken things a step further by offering full support for Brotli between client and server.That is, it does not first decompress the data before sending it to the user, but can retransmit compressed data directly.

Previously, Cloudflare used Brotli at level 4. Now it allows you to use level 11 if the origin server also supports that setting, optimizing performance.

In addition, it has a feature called Compression Rules which allows you to customize what content is compressed and how it is compressed, based on extension, type, domain, etc.

The only caveat is that features like Rocket Loader or Email Obfuscation can interfere. In these situations, the contents are decompressed and recompressed using Brotli level 4 for compatibility.

Precautions when using Brotli

Despite its benefits, it is important to keep in mind some considerations:

• Brotli only works on HTTPS connectionsIf your website uses HTTP, this will not apply.
• High compression levels (10-11) consume more CPU resources, which can affect server performance if there are many simultaneous requests.
• Some older hosting configurations do not support Brotli or require additional settings., especially on Apache servers without mod_brotli module.

Anyway, improvements in speed, SEO, user experience and bandwidth savings more than compensate for these limitations. Optimizing web performance is essential to offering a better experience and improving search engine rankings. Brotli compression, which is increasingly adopted, significantly reduces the size of HTML, CSS, and JS files, positioning itself as one of the benchmark algorithms for the modern web. If you don't yet have it enabled on your WordPress or server, we recommend considering it, as it's a free, open-source solution with verifiable benefits in speed and data efficiency.