No app required
There is nothing to install. Open the site, tap the upload area, pick an image from your photo library or Files, and convert. The result downloads directly to your device.
Where files land
On iPhone, converted files save to the Files app (or Photos for image formats iOS recognises). On Android they go to your Downloads folder. Zip archives from batch conversions can be opened natively on both.
Saving a .webp on mobile
Both iOS and Android display WebP natively, which is often how people end up with one — long-pressing an image on a web page saves whatever the site served, and most sites now serve WebP.
Add it to your home screen
The site can be installed as a home-screen shortcut on both platforms for one-tap access, without the storage cost of a native app.