The Settings features are your primary optimization tools.
Image Sizes
The Image Sizes feature allows admins to choose which thumbnails they want to be compressed and which ones Smush should ignore.
In order to serve scaled images, WordPress generates multiple copies in different sizes of every uploaded image. Some themes and plugins also require copies. These copies, called thumbnails, can add up quickly, so we recommend you compress all thumbnails.
Pro Tip
WordPress duplicate images are a net positive for most users – a simple exchange of storage space for faster page speed. WordPress pros, on the other hand, achieve page speed in many ways and the benefits of duplicate images may be minimal. Follow the Learn More link for guidance on preventing WordPress from creating multiple copies of your uploaded images.
Click Custom to reveal a list of the thumbnail sizes that WordPress is creating on your site. Select the checkboxes for the images you want to be compressed, and leave those you don’t want compressed unchecked. The image sizes you select will be compressed automatically upon upload if you have Automatic Compression enabled.
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