Batch Image Optimizer
What it is
A one-click tool that resizes and compresses every image already sitting in your media library, and — where possible — converts them to a modern, smaller image format automatically.
Why it matters
Every new image you upload is already optimized the moment it arrives, so you rarely think about this day-to-day. But if you ever change your optimization settings, or you're bringing over a media library from an older site (or an older version of your own), you can end up with a backlog of images that are bigger and slower to load than they need to be. Large, unoptimized images are one of the most common reasons a site feels sluggish — this tool cleans that up in bulk instead of leaving you to re-upload everything by hand.
How to use it
Open Tools → Image Compression and start the batch. It runs through your entire media library using the same resolution and quality settings configured in Settings → Images, so whatever balance of size versus quality you've already chosen applies consistently, past uploads included.
Once a batch starts, let it finish — it works through your whole library in one pass, and closing the tab partway through can leave some images processed and others not.