How Apple made Safari about 60% faster in the last 6 months

A month ago, we told you about the release of Speedometer 3.0, a new web performance testing benchmark that aims to provide a more fair and representative measure of how a web browser performs at modern web tasks. Unlike earlier versions of Speedometer, which were made more or less by Apple’s WebKit team, version 3.0 is made in a collaboration between Apple, Google, Microsoft, and Mozilla with a new governance model to agree upon what tests are important representations of the modern web.

In other words, it’s probably the most “fair” and up-to-date measurement of web browser performance we have right now.

WebKit is the rendering engine used by Safari and provided to Apple developers who wish to use web rendering within their apps. It’s required to be used by every browser on iOS or iPadOS except for those inside the EU. Apple’s WebKit development team published a blog post detailing how they used Speedometer 3.0 as a guide to optimize performance from Safari 17 (released in September 2023) and Safari 17.4 (released in March 2024).

Over those six months, a lot of small incremental improvements made a big difference. As the blog post summarizes:

With all these optimizations and dozens more, we were able to improve the overall Speedometer 3.0 score by ~60% between Safari 17.0 and Safari 17.4. Even though individual progressions were often less than 1%, over time, they all stacked up together to make a big difference. Because some of these optimizations also benefited Speedometer 2.1, Safari 17.4 is also ~13% faster than Safari 17.0 on Speedometer 2.1. 

WebKit blog post

Some of those improvements include things like batching compositing layer updates, increasing cache size on macOS, improving inline and SVG layout, and more. Many of these improvements are minor, resulting in just a few percentage points here or there, or targeting very specific parts of web performance. But multiple small improvements compounding over time made for a much faster browser.

This doesn’t mean Safari is much faster than other Mac browsers, though. When we tested Speedomenter 3.0 last month, we were running Safari 17.4 and found it to be the fastest browser but only by a very small margin. Edge still had some catching up to do, but Chrome and Firefox are both just behind Safari’s Speedometer score.