External Library updates in WordPress 5.5: call for testing

Edit 7/1/20: The post initially indicated that a minified version of Moment.js was now included in CoreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress.. This was incorrect, a minified version has always been included, but as a direct copy from upstream. That copy now has a sourceMappingURL reference (which is not desired). For that reason, the library is now minified in the Core build process instead. That sentence was removed to prevent confusion. Props @sergeybiryukov for catching that.

Edit 7/2/20: After this note was published, new versions of the Moment.js and getID3 libraries were committed. The version updates for each have been adjusted appropriately.

WordPress 5.5 is currently slated to bring some long awaited updates to a handful of external libraries bundled with Core. A few of the updates are particularly large, and while backwards compatibility measures were taken, they could potentially require adjustments to plugins, themes, and custom code. For that reason, this developer note also doubles as a call for testing.

Please help test these library updates, and report back any bugs to help ensure that no edge cases were missed during the initial testing.

You can test these changes by installing the WordPress Beta Tester 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 WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party (choose the “bleeding edgebleeding edge The latest revision of the software, generally in development and often unstable. Also known as trunk. nightlies” option), or download the nightly package directly (regenerated from trunk daily).

Remember, running the nightly version of WordPress is not recommended for production environments. Consider setting up a local development environment to test instead.

A full list of External Library tickets can be found on Trac, but below are the library updates currently slated to ship with WordPress 5.5, including all of the details you need to be aware of. The libraries that require an extra keen attention to detail are marked “please test”.

PHPMailer (please test)

Because of conflicting PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher support policies (support for PHP < 5.5 in was dropped in newer versions of the PHPMailer library), WordPress Core has been stuck on the 5.x version of PHPMailer for quite some time, even though a newer, 6.x version exists. However, now that WordPress only officially supports PHP back to version 5.6.20, PHPMailer can finally be updated.

This is a major update to the library. Please help by testing this update to ensure any edge cases are discovered.

Plugins that appear to be utilizing the library will soon receive an email to test their code. Below is what you need to know about the changes as they relate to WordPress Core.

Note: this is not an exhaustive list. For a more complete list of changes, please consult the Upgrading from PHPMailer 5.2 to 6.0 guide.

New file locations

To make updating the library easier, the PHPMailer files have been moved into the wp-includes/PHPMailer directory. The old files will remain for backwards compatibility and load the new corresponding files, but loading them will now throw a _deprecated_file() warning.

  • wp-includes/class-phpmailer.php is replaced by wp-includes/PHPMailer/PHPMailer.php.
  • wp-includes/class-smtp.php is replaced by wp-includes/PHPMailer/SMTP.php.

Additionally, the phpmailerException class is now separated into its own file, wp-includes/PHPMailer/Exception.php (previously, it was included at the bottom of the class-phpmailer.php file). When loading the PHPMailer library, the Exception.php file is required, and should also be loaded. If the old class-phpmailer.php file is loaded, the exception class will be loaded automatically to minimize failures.

New PHPMailer namespace

In past versions, the PHPMailer class existed within the global space. However, moving forward, the PHPMailer library is under the new PHPMailer\PHPMailer namespace. Below is an example of the old usage, and an example of the new way to utilize the library.

Old method

require_once ABSPATH . WPINC . '/class-phpmailer.php;
$phpmailer_instance = new PHPMailer();

New methods

Both examples will produce identical results.

use PHPMailer\PHPMailer\PHPMailer;
require_once ABSPATH . WPINC . '/PHPMailer/PHPMailer.php;
require_once ABSPATH . WPINC . '/PHPMailer/Exception.php;
$phpmailer_instance = new PHPMailer();
require_once ABSPATH . WPINC . '/PHPMailer/PHPMailer.php;
require_once ABSPATH . WPINC . '/PHPMailer/Exception.php;
$phpmailer_instance = new PHPMailer\PHPMailer\PHPMailer();

Similar changes must also be made when utilizing the PHPMailer Exception class.

The old classes have been registered as aliases of the new, properly namespaced classes using class_alias() in PHP (this is true for the PHPMailer, phpmailerException and SMTP classes). This means that a plugin containing code similar to the “old method” will continue to work seamlessly until it can be updated (with the exception of the _deprecated_file() notice).

Note: the aliases will only exist if the old, deprecated files are included. A plugin relying on Core to load the PHPMailer library will not have an alias present as the new files are now loaded instead.

Deprecated elements have been removed

Another big change in the 6.x update was the removal of all deprecated properties and methods. A full list of removed elements can be found in the upgrade guide.

Plugins using PHPMailer

All plugins that appear to be utilizing PHPMailer will soon be receiving an email notification to test their code and make any necessary adjustments.

For more information, check out the full list of changes included with this update, the PHPMailer 6.0 upgrade guide, or the related TracTrac An open source project by Edgewall Software that serves as a bug tracker and project management tool for WordPress. tickets (#41750, #50379, #50380).

SimplePie (please test)

SimplePie is a RSS and Atom feed framework bundled with WordPress Core to handle the consumption of RSS and Atom feeds. The library has remained largely untouched for several years, but has been updated from version 1.3.1 to the latest version (1.5.5) for WordPress 5.5.

This update includes 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, compatibility fixes for newer versions of PHP, added support for additional date formats, and minor improvements to ensure that feeds continue to be parsed correctly. Support for caching feed data to Redis and Memcached has also been added.

It is highly recommended that you test your code if your site fetches and processes RSS/Atom feeds.

Plugin authors were previously notified to test their code against the 1.5.5 update in early May, and the authors of plugins that were identified as using SimplePie should have received an additional follow up email. While no issues have been reported so far, it’s still possible that there may be undiscovered edge cases.

For more information, check out the full list of changes in SimplePie 1.3.1 to 1.5.5, or the related Trac ticketticket Created for both bug reports and feature development on the bug tracker. (#36669).


Earlier this year, the Unicode Consortium announced that Emoji v13.0 had been finalized. In addition to the 62 brand new emojis that were added, 55 gender and skin-tone variants were also added.

Platforms will begin rolling out native support later this year. But why wait? The Twemoji library has already been updated to support the new emojis, and that update will be included in WordPress 5.5.

So start spicing up your blogblog (versus network, site) about ninja (🥷) techniques, using tamales (🫔) and olives (🫒) on your food blog, and beavers (🦫) or polar bears (🐻‍❄️) on your wildlife blog.

For more information, check out the full list of new emojis added in Emoji v13.0, the Twemoji 13.0 release notes, or the corresponding ticket on Trac (#50148).

Masonry & imagesLoaded

The Masonry library has been updated from version v3.3.2 to 4.2.2, and the related imagesLoaded library has been updated from v3.2.0 to v4.1.4.

The biggest change in this update is the removal of support for IE versions 8 & 9. Core has not supported these versions of IE since WordPress 4.8, but if supporting these versions of Internet Explorer is important to your user base, please explore enqueuing your own versions of these libraries instead.

For more information, check out the full list of changes in Masonry, the full list of changes in imagesLoaded, or the related Trac ticket (#37675).


The getID3 library has been updated from version v1.9.18 to v1.9.20. This is a minor update that fixed several bugs. These fixes included one that caused a PHP notice when using PHP 7.4 and processing MP3 audio files.

For more information, check out the full list of changes in getID3 or the related Trac ticket (#49945).


The Moment.js library has been updated from version 2.22.2 to 2.27.0. For more information, check out the full list of changes in Moment.js, or the related Trac ticket (#50408).


The clipboard.js library has been updated from version v2.0.4 to v2.0.6. For more information, check out the related Trac ticket (#50306).

Props @earnjam for technical review, @newyorkerlaura and @justinahinon for proof reading.

#5-5, #dev-notes, #external-libraries