WordPress 6.4 Performance Improvements

WordPress 6.4 is the third major releasemajor release A release, identified by the first two numbers (3.6), which is the focus of a full release cycle and feature development. WordPress uses decimaling count for major release versions, so 2.8, 2.9, 3.0, and 3.1 are sequential and comparable in scope. of the year that delivers a better user experience to site visitors by improving performance of the coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress. software. This version improves server response time by ~4% over version 6.3.2. This, combined with additional frontend optimizations, leads to improvements to Largest Contentful Paint (LCP)—an important Core Web Vital. For example, Twenty Twenty-One (a classic theme) shows an improvement of ~4% for LCP and Twenty Twenty-Three (a blockBlock Block is the abstract term used to describe units of markup that, composed together, form the content or layout of a webpage using the WordPress editor. The idea combines concepts of what in the past may have achieved with shortcodes, custom HTML, and embed discovery into a single consistent API and user experience. theme) shows a ~9% LCP improvement when run on WordPress 6.4 compared with 6.3.2 based on benchmarks conducted by the WordPress Performance team.

This release caps off an ambitious year of work for the Performance Team, with major improvements made in each release. You can read more about those improvements in the performance improvement summary posts for version 6.2 and version 6.3. While version 6.2 focused on server side improvements, and 6.3 focused more on client side improvements, this release was focused on continuing server side improvements while further optimizing and extending the improvements that were made earlier in the year. Meanwhile, the team continued iterating on the tools and methodologies used to measure and report on performance.

Performance highlights for this release

An overview of the performance enhancements in this release is included in the WordPress 6.4 Field Guide and you can read details about the following highlights in their individual dev-note posts:

Server side improvements

Client side improvements

Evolving our benchmarking methodology

Previous performance benchmarks reported for each release were taken by @flixos90 (the performance release leadRelease Lead The community member ultimately responsible for the Release.) on his own computer, using a standardized set of best practices and tools. This release we have attempted to automate the process in order to establish a reproducible methodology that can be used by any contributor using a standard set of tools. 

The process for this release uses the compare-wp-performance GitHubGitHub GitHub is a website that offers online implementation of git repositories that can easily be shared, copied and modified by other developers. Public repositories are free to host, private repositories require a paid subscription. GitHub introduced the concept of the ‘pull request’ where code changes done in branches by contributors can be reviewed and discussed before being merged be the repository owner. https://github.com/ action, originally developed by @swissspidy, which sets up two standard test sites using wp-env inside of a GitHub worker, takes a set of metrics based on 100 requests, and reports them in the action summary (example). To account for variance between each run, this is done 5 times and the median values are used for reporting purposes.

Revisiting previous releases

Since the testing environment has an important impact on performance benchmarks, we wanted to revisit the previous versions from this year and apply the same methodology for comparison. Each of the following metrics show the percentage the metric either improved (negative numbers) or got worse (positive numbers) between versions.

WordPress 6.2.3 vs 6.1.4

Twenty Twenty-One 

  • LCP: +2.87%
  • Server Timing -4.21%

Twenty Twenty-Three

  • LCP: -4.72%
  • Server Timing -18.15%

WordPress 6.3.2 vs 6.2.3

Twenty Twenty-One 

  • LCP: -10.82%
  • Server Timing -3.34%

Twenty Twenty-Three

  • LCP: -14.23%
  • Server Timing -10.21%

WordPress 6.4.0 vs 6.3.2

Twenty Twenty-One 

  • LCP: -3.95%
  • Server Timing -4.05%

Twenty Twenty-Three

  • LCP: -9.06%
  • Server Timing -4.59%

Detailed data can be found in this spreadsheet, with links to the individual GitHub workflows.

Future improvements

While the methodology used for this release is an improvement over the previous process, there is much room for improvement, including finding ways to stabilize the metrics collected during benchmarks for releases and during development, improving the test content and use cases we test for these benchmarks, testing different configurations and environment characteristics (e.g., PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher versions, persistent object cache, etc.).


Props to @joemcgill for taking the time to write this extensive and detailed post, and @flixos90 for review.

#6-4, #core, #core-performance, #performance