WordPress Drop-In Plugins?

You know all about WordPress plugins and may have heard of Must-Use plugins, but what about “Drop-Ins”? In WordPress, there are three types of plugins: The list is very specific and, in many cases, providing a quick replacement to an error page where it may not make sense to try to add via hooks or filters. The kicker is the caching ones—advanced-cache.php or object-cache.

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