Photostack is an open-source batch photo editor that executes entirely in the browser. It supports watermarking and is compatible with all major web browsers. Multiple photos can be imported from a local storage device, an external web server, or Dropbox. You can then resize images, set the desired format, add a watermark and remove the EXIF data. Watermarks can be easily created in PhotoStack for use later if you wish to protect your images. PhotoStack does not restrict your choice of platform or require a monthly fee. The software is compatible with all modern web browsers. The entire source code is available on GitHub under the GPLv3 license. Images are processed locally in your browser. PhotoStack does not upload any photos anywhere, and the only data it collects is basic analytics. Thanks to a web technology known as Service Workers, PhotoStack can operate entirely offline on most browsers. PhotoStack is compatible with most modern browsers and platforms that support current web features, including Chrome, Firefox, Opera, Microsoft Edge.
On the 16th of October, PhotoStack added JPEG XL support. You can use the JPEG XL format as you would use any other image file.