A plugin is a self-contained piece of software that integrates with a host program through a defined interface to add functionality. In web development the term most often refers to CMS add-ons, such as WordPress plugins, and to browser extensions.
Why it matters
Plugins let you add contact forms, caching or SEO tools in minutes. Each one also adds code that runs on your site, so quality varies: a poorly written plugin can slow pages, conflict with others or open a security hole. Conflicts after updates are a leading cause of broken CMS sites.
Example
To find a conflicting plugin on a WordPress site, deactivate all plugins, confirm the problem disappears, then reactivate them one by one while reloading the page. The one that brings the error back is the culprit. Doing this on a staging copy avoids downtime.
Common mistakes
- Installing a plugin for a tiny feature that a few lines of code would cover.
- Updating all plugins at once on a live site with no backup.
- Using abandoned plugins that have not been updated in years.
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