Most of WordPress users remove a plugin they previously installed by clicking the Delete button in their WP Admin -> Plugins -> Installed Plugins. However, does this remove the plugin from a site completely or are there any bits of it that are left behind? You guessed it right – sometimes, there are files and database entries that still remain even after the plugin has been uninstalled. This has its pros and cons but nevertheless, it does affect the site speed for sure!
Check out this great article which provides more information on the subject of properly uninstalling a WordPress plugin: