Improvements to Template Loading in WordPress 6.4

Improve performance of _register_theme_block_patterns() function

The _register_theme_block_patterns() function previously introduced a substantial resource overhead issue, especially noticeable when themes, such as Twenty Twenty Four, registered a large number of 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. patterns. This overhead was mainly due to the extensive file operations required by the function, including file system checks and file reads.

To address these performance issues, we have introduced caching using object cache in a new method called WP_Theme::get_block_patterns(). When theme development mode is disabled and a theme exists, the block patterns are stored in object cache. For sites using a persistent object cache, subsequent requests will use this cached data, eliminating the need for file lookups and reading files into memory, resulting in significant performance improvements.

It’s important to note that caches are also tied to the theme’s version number. Therefore, if you want to manually invalidate the cache, you can do so by changing the theme’s version number. This provides an additional method for cache management, especially useful during theme updates or changes.

Developers can bypass the pattern cache by enabling development mode for a theme, allowing for pattern additions and removals without the cache interfering. This is beneficial for accurate testing and development.

Cache invalidation occurs when themes are switched, the WP_Theme::cache_delete() method is called, or when the theme’s version number is updated. These mechanisms ensure that block patterns are not stored in the cache incorrectly.

Remove unnecessary checks if a theme file exists in the theme functions

In [56523] and [56357], WordPress theme functions were improved by removing unnecessary file existence checks, thereby enhancing performance and efficiency.

Previously, several functions and methods in the Themes 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. were designed to check for the existence of files within a child themeChild theme A Child Theme is a customized theme based upon a Parent Theme. It’s considered best practice to create a child theme if you want to modify the CSS of your theme. before falling back to the parent theme. 

However, these checks didn’t take into account whether the current theme was a child theme or not, leading to redundant file existence checks for non-child themes. This could result in unnecessary file system access and potentially slow down WordPress websites, especially in cases where there were numerous checks.

To address this issue and improve the overall performance of the Themes API, we’ve introduced an optimization that checks whether the current theme’s stylesheet directory matches the template directory before proceeding with file existence checks. This optimization significantly reduces the number of unnecessary file system accesses, as file existence checks can be resource-intensive in PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher.

As part of this enhancementenhancement Enhancements are simple improvements to WordPress, such as the addition of a hook, a new feature, or an improvement to an existing feature., we’ve updated the following functions and methods in WordPress:

  • WP_Theme::get_file_path()
  • get_theme_file_path()
  • get_theme_file_uri()
  • locate_template()

With these optimizations in coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress., you can expect a noticeable improvement in the performance of your WordPress theme, especially if you have a non-child theme. The reduction in unnecessary file system access can lead to faster page load times and a smoother user experience.

Tickets: #59279, #58576

Improve performance of get_block_theme_folders()

The get_block_theme_folders() function suffered from suboptimal performance due to repeated file lookups using the file_exists() function. This resulted in unnecessary I/O operations and slowed down the process of locating block template folders within themes.

To address these performance issues and improve the efficiency of the get_block_theme_folders() function, the following changes have been implemented:

  • A new method, WP_Theme::get_block_template_folders(), has been added which incorporates basic caching, storing the result in the theme’s cache, similar to how block themes are cached in the block_theme property (as outlined in [55236]). The introduction of caching significantly reduces redundant file system lookups and optimizes the overall performance of the function.
  • Improved Error Handling: This update enhances error handling by first verifying the existence of a theme before attempting to look up the file. This proactive error handling approach helps avoid unnecessary file checks and enhances the overall reliability of the function.


The performance enhancement in the WP_Theme::get_block_template_folders() method will lead to quicker and more efficient lookups 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.

Ticketticket Created for both bug reports and feature development on the bug tracker.: #58319

Bundled Theme: Implement the_header_image_tag() function for enhanced compatibility for older core themes.

The the_header_image_tag() function was introduced in WordPress 4.4 as part of [35594]. It is used in all themes created since WordPress 4.4 that supported headerHeader The header of your site is typically the first thing people will experience. The masthead or header art located across the top of your page is part of the look and feel of your website. It can influence a visitor’s opinion about your content and you/ your organization’s brand. It may also look different on different screen sizes. images. The function get_header_image_tag() continues to get updated with new image features, like lazy loading, async decoding and fetch priority. To ensure our core themes maintain compatibility and benefit from these enhancements, a backward compatibility shim has been applied, integrating the the_header_image_tag() function into the following core themes:

  • Twenty Ten
  • Twenty Eleven
  • Twenty Twelve
  • Twenty Fourteen
  • Twenty Sixteen

This change ensures future compatibility and modern image features are applied for header images to these older themes.

Ticket: #58675

Props to @spacedmonkey for writing this 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..
Props to @westonruter for editing, @mikeschroder and @webcommsat for reviewing.

Edit: The implementation for caching theme patterns during pattern registration was changed from transients to standard object caches after this dev note was first published (See [56978]). This post has been updated to reflect those changes.

#6-4, #dev-notes, #dev-notes-6-4, #performance