A plugin conflict is when two WordPress add-ons - or an add-on and your theme - don't get along, and something on your site breaks: a page won't load, a feature stops working, or the whole site goes down.
Also known as: Plugin incompatibility, conflicting plugins
In plain English
Plugins are built independently and often assume they're the only one touching a feature. When two of them (or a plugin and your theme) try to control the same thing - two SEO plugins both rewriting your titles, a form plugin fighting a page builder - the result is broken output, errors, or a white screen.
Why it matters for your business
Conflicts are the most common cause of "the site suddenly broke" after an update or a new install - and the hardest for non-developers to diagnose because the visible symptom rarely points at the cause. They're also why "just deactivate plugins one by one" is the classic first troubleshooting step.
When you'll run into it
Right after installing or updating a plugin or theme, when a specific page or feature stops working while the rest of the site is fine, or after any major WordPress update.
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