The code is not obfuscated so you can inspect it and see how it works - for uploaded image files, the work is done entirely by your browser!
Only the filename of the uploaded file and a log of buttons pressed goes to the server for analytics, so text only. The URL goes to the server to do the resize/crop if you submit an image by URL (URL is sent via proxy, has to work this way because of CORS.)
Made with love for the fun of it, no ads, no paid anything, it's totally free, any feedback would be awesome too.