Following is a list of cross-browser/platform web development and debugging tools useful for client-side developers. Depending on the application, one or all of these tools can be valuable in completing work on a website front-end.
Earlier today, while looking for a new solution to an older IE compatibility issue, I chanced across this nifty script for testing IE on macOS using virtual machines and VirtualBox: xdissent.github.com/ievms.
Developing for mobile? You’re gonna need an emulator. Here’s a list of emulators and simulators that can be used to test your mobile webapps.