On 28 June, the first test version of WordPress 6.3 (Beta 2) was released, which is actually the second since there was no Beta 1 due to technical problems with the packaging of the release and they opted to skip it in order not to delay the development schedule.
WordPress 6.3, scheduled for release on 8 August 2023, will be the last major release of phase 2 of Gutenberg's 4-phase project focused on customisation. 6.3 is supposed to close out many outstanding tasks related to full site editing (FSE) and usability in general.
It will also incorporate the ten most recent versions of the Gutenberg plugin, from 15.2 to 16.1.
Also new in Gutenberg 16.1 is the development of the new table of contents block that was added as an experimental block in Gutenberg 13.3.0 in November 2022.
What's new in these versions of Gutenberg and the optimisation improvements are the two points I'm most interested in, but mainly the performance-related ones, so I've been tinkering with it for a couple of days now.
Performance
WordPress 6.3 comes with more than 170 performance-related updates, continuing the plan of optimisation and performance improvements started in 6.1 and extended in 6.2.
Defer and async support has been added to the API. (Note that this has now closed a ticket that was opened 13 years ago) and fetchpriority support for images.
According to what we read, optimisations have been made for block template resolution, lazy load of images (Lazy Load) and emoji loader, all of which will contribute to better performance of the LCP. This, having a lot to do with the DOM, I'm guessing will quite possibly have some positive impact (not yet known to what extent) on INP, Google's new Core Web Vitals metric.
Compatibility with PHP versions 8.0, 8.1 and 8.2 has also been improved.
Now I'm still investigating everything to try to find the best way to get measurable results by comparison with 6.2.2
Remember that if you want to test Beta and RC to test the new stuff and make sure all your plugins and revamps are still working properly, the fastest and zero risk way is to use the WordPress Beta Tester plugin under a staging environment.
To do this, you install the plugin, select"Early Development", save and in the new options that will appear when you refresh, check"Beta/RC Only" and save again. After this you can update to the latest version and continue to receive notifications of the next versions.
