Photopea appears to do it properly with feature testing (no UA checks): https://www.photopea.com/willitwork/test.js https://www.photopea.com/willitwork/test.js

Photopea appears to do it properly with feature testing (no UA checks): https://www.photopea.com/willitwork/test.js https://www.photopea.com/willitwork/test.js FYI, Modernizr is a fantastic library for browser feature testing. You can just "add to cart" the tests you want to perform. No hand rolling necessary: https://modernizr.com/ https://modernizr.com/