So first off, what even is JQuery?
Cast your mind back 20 years and websites and the World Wide Web was largely still in its infancy, Internet Explorer 6 was shipping with Windows XP and if you weren’t a fan of Microsoft, you might be using Mozilla or even Netscape. In 2001 web page standards were at best lax and poorly adopted, and of those standards, the various browsers each adopted different standards and very few of the same.
This meant from a Web developer’s point of view, making a standardised set of web pages that would look and behave consistently across different browsers, was a challenge.
Web pages have always needed a way to run code within the browser to enrich the web page’s experience. In English, this might be scrolling images, elements of the page that show and hide, or simply being able to submit a form without re-submitting the whole page. These are all things we accept as the norm these days, and that’s largely due to JQuery.
JQuery took the inconsistencies of different browsers and created a way for developers to (in their own words) “do more with less code” and it worked!
Fast forward to 2021 and WordPress 5.5.
As a result, WordPress 5.5 took the move to remove support for JQuery Migrate which itself is a version of the JQuery libraries to bridge a compatibility gap with early JQuery code.
How do you fix this?
For now, it’s a very easy fix, this plug-in will add back in support for you.
I’ve installed the plug-in I get a load of errors?
Yes, you will, but you don’t need to worry. What the Plug-in is warning you is that there are still plug-ins that are using the old JQuery Migrate library. The developers of the plug-ins will in time remove their reliance on JQuery Migrate, but in many cases, this is far from a small job and is likely to take considerable time.
What can I do in the meantime?
Ensure your site is up to date, ignore the warnings and in time, one by one, they’ll disappear from your list of warning as each developer updates their code.