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Compress and compare images with different codecs, right in your browser
I use Squoosh to convert individual images to WEBP. I haven't found a good free bulk tool yet, and I still find I have to mess with the settings to make sure the image still looks good after being compressed.
Faster web pages and apps.
Image Optim: Mac only, can set custom compression settings and remove heavy metadata. I use this after resizing the images in Bulk Resize since the compression settings here are much more comprehensive.
Resize large photos in bulk
Bulk Resize Photos: Allows dragging and dropping of multiple images, setting max widths, converting pngs to jpgs, and a whole bunch of other actions that I used to have to do in Photoshop. I don't use the compression option here, only resizing.