How to install a WordPress plugin from a zip (and roll it back)

WordPress is the easiest of the five platforms to install on, and the easiest to break with a plugin that fights your theme. The install is two minutes; the discipline is in the backup.

1. Upload the zip itself

In wp-admin → Plugins → Add New Plugin → Upload Plugin, choose the .zip file. Do not unzip it first — the uploader wants the archive and will unpack it into wp-content/plugins/ for you.

Prefer FTP or your host's file manager? Then unzip into wp-content/plugins/ so that the plugin ends up as one folder, e.g. wp-content/plugins/your-plugin/, containing your-plugin.php.

2. Activate

Click Install Now, then Activate. The plugin may add its own menu item in the sidebar, or its settings may appear under Settings — read the plugin's own readme rather than hunting.

3. Check the site with a real browser

Activation succeeding is not the same as working. Open the front page and one post in a private window (so you are not served a cached admin view). A plugin that only breaks the front end is usually a theme conflict, and it will not show up in wp-admin.

The rollback that needs no backup

Deactivate, then delete. If the plugin's readme says it removes its tables on delete, deactivate and leave it installed instead — you keep the data and lose nothing but a few kilobytes.

If you already deleted it and want the data back, that is what the database dump is for. This is why the backup step comes before the install step and not after.

Things that will bite

• “The package could not be installed. No valid plugins were found.” — you zipped a folder containing a folder, or the plugin has no header comment in its main PHP file.
• Upload limit exceeded — raise upload_max_filesize and post_max_size, or upload by FTP.
• White screen after activation — PHP version. Deactivate by renaming the plugin folder over FTP; wp-admin comes back immediately.
• Auto-updates — a plugin that auto-updates can update itself into an incompatibility overnight. On a production board, update deliberately.

Keep the zip

The zip you installed is the version you tested. Keep it next to your backup, named with its version number, so "go back to what worked" is a file copy and not an archaeology project.