This summer’s WordPress hot news have been the update to version 5.5 that has brought countless new features of all kinds, most of them quite obvious and visible to users.
I am referring to the native sitemaps, block patterns, automatic updates of plugins and themes, plus lots of visual changes in the editor.
But all these changes, like it or not, have not been what has caused more attention and news, but the multitude of WordPress sites that have had problems, due to an internal change: the deactivation of the tool called jQuery Migrate.
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Thousands of broken or troubled WordPress sites
The result of this change has been that hundreds of thousands of WordPress sites have had all kinds of problems or even their website has broken down completely. And it’s all because part of their installation was working thanks to jQuery Migrate despite having obsolete code.
What is jQuery Migrate?
jQuery Migrate is a JavaSCript library that for years has allowed developers of themes and plugins to use obsolete jQuery code.
What it does is allow you to use obsolete code regardless of the version of jQuery installed by default in WordPress. This way, theme and plugin developers did not have to keep an eye on the jQuery version of WordPress, but this did not make much sense in a system where we are always insisting on having everything up to date, right?
Why has jQuery Migrate been removed from WordPress 5.5?
Because it was time, it’s about time that the software that works under WordPress uses the latest versions of JavaScript, and for this the WordPress development team defined a change in 3 phases, of which removing the jQuery Migrate tool is the first.
- 1st phase: Remove the previous version of jQuery Migrate to force developers to update their obsolete code.
- 2nd phase: Upgrade the version of jQuery included in WordPress from 1.4.1 to 1.9+
- 3rd phase: Upgrade jQuery Migrate included in WordPress to allow jQuery versions from 1.12.4 to 3.5+
How do I know if I can seamlessly upgrade to WordPress 5.5?
To check if your site will have no problems when upgrading to WordPress 5.5 you can/should install the Test jQuery Updates plugin.

This plugin disables the WordPress jQuery Migrate tool without having to upgrade to WordPress 5.5, so you can check if your site is still working properly or is generating errors.
If you install and activate the Plugin and everything seems to be fine and there are no errors in the browser console, you are ready to migrate to WordPress 5.5.
How can I upgrade to WordPress 5.5 when I still have outdated code?
Many times you will not be able to immediately update all the obsolete code, be it plugins, theme or custom, and that does not mean that you cannot update to WordPress 5.5, fortunately.
As a temporary solution to give site managers and developers time to update their obsolete code, the WordPress team has developed a Plugin that reactivates the jQuery Migrate Helper tool previous to WordPress 5.5.
Just install and activate Enable jQuery Migrate Helper and everything should work again.

This plugin and its growing number of installations is a clear sign that there were many WordPress with obsolete JavaScript code.
Once active, navigate through the different administration screens of your WordPress(posts, pages etc.) and, in case of error, a warning of the code that should be updated will be displayed.

You should then start taking steps to update the obsolete codes…
- Contacting the developer of the theme or plugin.
- Modifying the code if it was customized.
- Updating plugins and theme.
jQuery Migrate Helper shows no warnings but I have issues
If with the jQuery Migrate Helper plugin no warnings are shown but you detect issues in your WordPress operation you can also check the browser’s developer console.
Just right click anywhere on the screen where there are issues and activate the console.

Can I use jQuery Migrate Helper and forget about it?
Don’t even think about it!
This plugin is only a temporary solution and for WordPress 5.6 it will change everything again, so don’t rest on your laurels because with this active plugin you can continue using your WordPress website normally.
This Plugin only gives you a grace period to update Plugins, the theme, all the obsolete code.
Also, remember that using unupdated Plugins and themes is a high security risk, compromising your data and your entire website.
Once you detect which plugins, themes or custom codes generate issues you have to …
Check for theme updates and plugins compatible with new versions of jQuery.
Update any custom code to new jQuery versions.
The paging error after upgrading to WordPress 5.5
A rather recurrent issue has been the paging that stopped working. This has been due to the way many topics applied the pagination parameter.
According to the report in the WordPress error log it was due to the way the query was made.
In this case the solution is clearly to ask the developer of your theme to update it.
Read this post in Spanish: Errores tras actualizar a WordPress 5.5 ¿hay solución?