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WebP works in every current browser, and in Safari from version 14. Safari only shows AVIF from version 16. To serve older Apple devices as well, choose WebP or the fallback mode. There, with AVIF, Safari 14 and 15 get the WebP copy, and a browser that knows neither gets the original file.

WebP, for almost every site. AVIF is smaller but much slower to create, and Safari 15 and older, many social media link previews and most e-mail clients do not show it. If you do go for AVIF, use the fallback mode.

Yes. Clear your CDN cache after converting, because the plugin cannot do that for you. If your database contains URLs with your CDN host name, add that host with the verklein_rewrite_hosts filter. With <picture> in fallback mode a CDN needs nothing else. If you use the Accept-header rule, your CDN must respect the Vary: Accept header, or an old browser may still get the WebP. The System check tests that rule.

nginx ignores the .htaccess file that closes the backup folder, so add a rule to your server configuration yourself. The second rule passes old JPG and PNG URLs to WordPress, for the 301 redirect. The exact folder name is on the System & help tab, and the System check tests whether the folder is closed. The rules are in the documentation.

Yes, as long as the originals are in the backup folder or were left in place, which is the default. Go to verklein.nu → Restore & clean up, restore single images in the Media Library, or use wp verklein restore. Once you have deleted the backups, or had the originals deleted, it is no longer possible.

While converting, the new files sit next to the old ones, and the originals are kept as a backup. So count on some extra space for a while. Once you are happy, delete the backups and only the smaller files remain. In fallback mode the original and the copy both stay. The System check shows how much space is free.

Yes. The URL update handles plain text, HTML, JSON with escaped slashes and serialized PHP data, the way Elementor, Divi, Beaver Builder, Oxygen, Bricks, WPBakery and Avada store them. The CSS cache of Elementor, Beaver Builder, Divi and Avada is cleared automatically. On Oxygen, regenerate the CSS cache under Oxygen → Settings.

Smaller images load faster, which is good for how quickly your pages load. The title, alt text and ID of your images stay the same. In replace mode the file name changes from .jpg to .webp, but the plugin can redirect old URLs with a 301, so links from other sites and Google Images keep working.

Both work. Imagick is preferred: it gives better quality, keeps colour profiles and supports the effort setting. Whether your server can create AVIF depends on how Imagick or GD was built. The System check tells you; if not, your host can usually switch it on.

Creating AVIF files takes a lot of computing. Expect 3 to 20 seconds per image including every size, against half a second to two seconds for WebP. A large library can take hours. Set the effort to 3 or 4 on slow hosting, and use WP-CLI for thousands of images.

Only for files that are still on your own server. With WP Offload Media, Media Cloud or WP-Stateless the plugin warns you up front, and it does not upload the converted files to the cloud.

Your converted images, the copies from fallback mode and the backup folder always stay, so your site keeps working. In fallback mode it shows the original JPGs and PNGs again. Settings and restore data are kept by default too, so you can still restore after reinstalling. To remove everything, first switch on Remove all plugin data when the plugin is deleted in the settings. To go back to the originals, restore before you delete the plugin.