Replacing hard-coded style tags with wp_add_inline_style()

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. 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(). This change was implemented to address issues related to redundant code and bypassing the coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress.’s style enqueuing system, which made it challenging for third-party developers to manage and control the output of style tags.

Deprecated Functions

To maintain backward compatibility, the following functions have been deprecated and replaced with the new approach:

  • print_embed_styles()
  • print_emoji_styles()
  • wp_admin_bar_header()
  • _admin_bar_bump_cb()
  • the_block_template_skip_link()

Backwards Compatibility Unhooking

Previously, when wanting to unhook certain functions like print_embed_styles() from happening at wp_print_styles(), a theme or pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the Plugin Directory or can be cost-based plugin from a third-party would do:

remove_action( 'wp_print_styles', 'print_emoji_styles' );

In 6.4 this print_emoji_styles() function is now deprecated. Nevertheless, the above method for preventing emoji styles from being printed is retained, even though they are now being printed by wp_enqueue_emoji_styles(). This applies to the other deprecated functions as well, so no developer action is required.

Developer Action Required

For developers who are currently using the wp_print_styles() function, whether it’s in unit tests or within their own code, some adjustments may be necessary to ensure a smooth transition. You should follow the example set by 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. This is what you need to do:

 * Remove the deprecated `print_emoji_styles` handler.
 * It avoids breaking style generation with a deprecation message.
$has_emoji_styles = has_action( 'wp_print_styles', 'print_emoji_styles' );
if ( $has_emoji_styles ) {
    remove_action( 'wp_print_styles', 'print_emoji_styles' );

$styles = ob_get_clean();

if ( $has_emoji_styles ) {
    add_action( 'wp_print_styles', 'print_emoji_styles' );

This code snippet demonstrates how to handle the situation. It first checks if there’s an action hooked to wp_print_styles for print_emoji_styles(). If it does exist, it removes the action temporarily to avoid issues with style generation.

By following this approach, you can ensure that your code remains compatible with the changes introduced in this commit while avoiding any disruptions to style generation. It’s recommended to review and adjust your code accordingly if you’ve been using the wp_print_styles() function.


In the case of the functions for printing custom backgrounds and custom styles, converting them to use inline styles was deemed infeasible. Changing the style 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.) IDs in this context could potentially disrupt JavaScriptJavaScript JavaScript or JS is an object-oriented computer programming language commonly used to create interactive effects within web browsers. WordPress makes extensive use of JS for a better user experience. While PHP is executed on the server, JS executes within a user’s browser. functionality for several plugins in the repository. Therefore, these functions remain unaffected by this change.

Please refer to #58775 for additional details on these changes.

Props to @spacedmonkey for writing the dev note.
Props to @westonruter, @flixos90, @webcommsat, and @bph for review and proofreading.

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