Appetize.io
Cloud iOS simulators and Android emulators in the browser
AWS Device Farm
Testing on real mobile devices and desktop browsers hosted on AWS
HeadSpin
Real-device testing of mobile, web and OTT apps
Selenoid
Selenium hub running browsers in Docker containers (unmaintained)
UI Verify
Visual testing for coding agents: catch UI regressions on every pull request
pixelmatch
Pixel-level image comparison library