WordPress 6.4 Field Guide

This guide shares more in-depth changes that you will find in 6.4 and is published in the Release Candidaterelease candidate One of the final stages in the version release cycle, this version signals the potential to be a final release to the public. Also see alpha (beta). cycle to help inform WordPress developers, extenders, and others. The release squad and many contributors across the global project have worked to bring these changes, and you can follow this work and add to the contribution using the ticketticket Created for both bug reports and feature development on the bug tracker. systems in Trac and 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/.

Some fascinating stats! TracTrac An open source project by Edgewall Software that serves as a bug tracker and project management tool for WordPress. has about 268 tickets, 113 of which are enhancements and feature requests, 134 bug fixes, and 21 other tasks. This time, there are more than 64 tickets with a focus on performance, 17 for accessibility, and 16 for modernizing code and applying coding standards. GutenbergGutenberg The Gutenberg project is the new Editor Interface for WordPress. The editor improves the process and experience of creating new content, making writing rich content much simpler. It uses ‘blocks’ to add richness rather than shortcodes, custom HTML etc. https://wordpress.org/gutenberg/’s GitHub repo brings more than 1,400 updates/changes, providing to coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress. more than 420 enhancements, 445 bugbug A bug is an error or unexpected result. Performance improvements, code optimization, and are considered enhancements, not defects. After feature freeze, only bugs are dealt with, with regressions (adverse changes from the previous version) being the highest priority. fixes, and 42 accessibility improvements.

Changes in 6.4 are spread across about 45 core components. Below is the breakdown of the most important ones.

You can also find all Developer Notes relating to 6.4 as they continue to be published until the release goes live. You can follow them using this tag.

Updated Nov 14, 2023: overview posts available on accessibility and performance improvements in 6.4.

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. editor

WordPress 6.4 is bringing six Gutenberg releases into the core – 16.2, 16.3, 16.4, 16.5, 16.6, 16.7. You will find Block HooksHooks In WordPress theme and development, hooks are functions that can be applied to an action or a Filter in WordPress. Actions are functions performed when a certain event occurs in WordPress. Filters allow you to modify certain functions. Arguments used to hook both filters and actions look the same., the ability to register their own media categories, changes to the @wordpress/components package, updates for the user interface components, and many other changes.

WordPress 6.4 introduces Block Hooks (#53987), a feature that provides an extensibility mechanism for Block Themes. This is the first step in emulating WordPress’ Hooks concept that allows developers to extend Classic Themes using filters and actions.

From WordPress 6.4, extenders can register their own inserter media categories and provide users with more options from which to choose.

6.4 brings in a number of notable changes to the @wordpress/components package.

There are a number of other changes, including a new background image block support, fluid typography, disabled layout controls globally or on a block basis by theme.json, Stabilized APIs for InnerBlocks, and much more.

New dev notedev note Each important change in WordPress Core is documented in a developers note, (usually called dev note). Good dev notes generally include a description of the change, the decision that led to this change, and a description of how developers are supposed to work with that change. Dev notes are published on Make/Core blog during the beta phase of WordPress release cycle. Publishing dev notes is particularly important when plugin/theme authors and WordPress developers need to be aware of those changes.In general, all dev notes are compiled into a Field Guide at the beginning of the release candidate phase. (November 13, 2023) – For singular content, the output of block templates, for example, (single.html or page.html) will be automatically wrapped in the main query loopLoop The Loop is PHP code used by WordPress to display posts. Using The Loop, WordPress processes each post to be displayed on the current page, and formats it according to how it matches specified criteria within The Loop tags. Any HTML or PHP code in the Loop will be processed on each post. https://codex.wordpress.org/The_Loop..

Adminadmin (and super admin) notices

Two new functions abstract the HTMLHTML HyperText Markup Language. The semantic scripting language primarily used for outputting content in web browsers. markup generation to reduce the maintenance burden, encourage consistency, and enable argument and message filtering for all admin notices used widely in WordPress Core and the extender community.


A developer note will be added later on the following change:

Introduce wp_trigger_error() to complement _doing_it_wrong() #57686

HTML APIAPI An API or Application Programming Interface is a software intermediary that allows programs to interact with each other and share data in limited, clearly defined ways.

WordPress 6.4 includes continued development of the HTML API, including the introduction of a minimal HTML Processor with the concept of breadcrumbs, and makes it possible to, for example, search for images that are direct children of a DIV.

Also included in 6.4, is the addition of a couple of CSSCSS Cascading Style Sheets./class helpers in the Tag Processor, which will make it possible to search for a tagtag A directory in Subversion. WordPress uses tags to store a single snapshot of a version (3.6, 3.6.1, etc.), the common convention of tags in version control systems. (Not to be confused with post tags.) containing more than one class name, or to search for a tag not containing a given class name.


New WordPress installations will now have attachment pages fully disabled for new sites. This will benefit SEO by avoiding attachment pages created by default, which were indexed by search engines and could have led to bad results for users and site owners. The change introduces a wp_attachment_pages_enabled database option to control the attachment pages’ behavior. In the dev note, there is information on how to update existing sites.

Additional performance improvements

A significant part of the 6.4 release brings performance improvements and greater efficiency to WordPress. An overview post on performance improvements in 6.4 is also available.

New functions get_options(), wp_prime_option_caches(), and wp_set_option_autoload_values() allow an enhanced performance of retrieving options from the database.

WordPress 6.4 brings many improvements to template loading.

  • Performance gains have been achieved by introducing caching using an object cache in a new method called WP_Theme::get_block_patterns().
  • Unnecessary checks were removed if a theme file existed in the theme functions that enhanced efficiency and performance. These improvements in the Themes API mean the current theme’s stylesheet directory is checked to ensure it matches the template directory, before further file existence checks are done. Improvements are also in the performance of get_block_theme_folders(). This is through a new method, WP_Theme::get_block_template_folders(), and improved error handling. The result is a quicker and more efficient lookup of block template folders within themes. WordPress developers and users can anticipate improved performance, reduced I/O overhead, and a smoother experience when working with block themes.

Improved image loading

Several enhancements to the wp_get_loading_optimization_attributes() function, which provides a central place to manage loading optimization attributes, specifically for images and iframes. 

Script Loader

In WordPress 6.4, script loading strategies are now employed for frontend scripts in core and bundled themes. For the most part, the defer loading strategy is used since it is more consistent in its loading behavior, in that a defer script always executes once the DOM has loaded; a script with async may actually block rendering if it is already cached. Additionally, loading with defer has been moved from the footer to the head so that they are discovered earlier while the document is loading and can execute sooner once the document is loaded.

Style loading

This dev note highlights the changes made in WordPress 6.4 to style loading. The main focus of the changes was to replace manually created style tags printed at the wp_head action with calls to wp_add_inline_style().

More performance-related changes

  • TaxonomyTaxonomy A taxonomy is a way to group things together. In WordPress, some common taxonomies are category, link, tag, or post format. https://codex.wordpress.org/Taxonomies#Default_Taxonomies.: The double sanitization in the get_term function has been stopped. This will prevent the unnecessary calls to sanitize_term, which was detrimental to performance. Trac ticket #58329.
  • Themes: The TEMPLATEPATH and STYLESHEETPATH constants have been deprecated. get_template_directory() and get_stylesheet_directory() should be used instead. Trac ticket #18298

And there’s more!

Some of the additional changes in 6.4 to highlight.

External libraries

jQuery has been updated to version 3.7.1. This release fixes a regressionregression A software bug that breaks or degrades something that previously worked. Regressions are often treated as critical bugs or blockers. Recent regressions may be given higher priorities. A "3.6 regression" would be a bug in 3.6 that worked as intended in 3.5. from jQuery 3.6.0 that resulted in rounded dimensions for elements in Chrome and Safari. Also, a (mostly) internal Sizzle method, jQuery.find.tokenize that was on the jQuery object was accidentally removed when they removed Sizzle in jQuery 3.7.0. That method has been restored.

Trac Ticket #59322


WordPress 6.4 brings a number of key improvements to the HTML markup of the wp-login.php page to make its structure more optimal and allow developers to have more customized individual styling flexibility. #30685

Clarify the “Add New” links in the Admin for better accessibilityAccessibility Accessibility (commonly shortened to a11y) refers to the design of products, devices, services, or environments for people with disabilities. The concept of accessible design ensures both “direct access” (i.e. unassisted) and “indirect access” meaning compatibility with a person’s assistive technology (for example, computer screen readers). (https://en.wikipedia.org/wiki/Accessibility)

In WordPress 6.4, the default values for the add_new label changed to include the type of content. This matches add_new_item and provides more context for better accessibility. The default value is ‘Add New Type’ for both hierarchical and non-hierarchical types. If you’ve previously used a label such as:

'add_new' => _x( 'Add New', 'Book', 'my-plugin' )

you are encouraged to change it to

'add_new' => __( 'Add New Book', 'my-plugin' )

Trac ticket #47125

Props to @swissspidy for this dev note.

Integration testing requirement change

PHPUnit Polyfills 1.1.0 is required for running integration tests with WordPress 6.4.

Trac ticket #59510

Props to @jrf for the information for this dev note.

HTTPHTTP HTTP is an acronym for Hyper Text Transfer Protocol. HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. API

  • HTTP API: WP_Http_Curl and WP_Http_Streams classes and filters have been deprecated as these classes have not been used in WordPress Core since the introduction of the Requests library. Trac ticket #58705

RevisionsRevisions The WordPress revisions system stores a record of each saved draft or published update. The revision system allows you to see what changes were made in each revision by dragging a slider (or using the Next/Previous buttons). The display indicates what has changed in each revision.

Revisions are now supported for post metaMeta Meta is a term that refers to the inside workings of a group. For us, this is the team that works on internal WordPress sites like WordCamp Central and Make WordPress. on an opt-in basis. Trac ticket #20564

Props to @costdev, @bph, @nalininonstopnewsuk, @codente, @spacedmonkey, @desrosj, @flixos90 for input on this Field GuideField guide The field guide is a type of blogpost published on Make/Core during the release candidate phase of the WordPress release cycle. The field guide generally lists all the dev notes published during the beta cycle. This guide is linked in the about page of the corresponding version of WordPress, in the release post and in the HelpHub version page., and @joemcgill, @clarkeemily, @cbringmann, @akshaya, @611shabnam, and @priethor for peer review.
Thank you to all those involved in collating, writing, and editing developer notes relating to 6.4.

#6-4, #dev-notes, #dev-notes-6-4, #field-guide