Steam ID Finder

The new innovation is here!
Simply visit a Steam profile page and instantly copy the player ID that you need!
Also – it’s possible to just right-click any player to instantly copy the desired ID!
You can even visit the Friends Manager page and instantly copy all of your friends’ IDs in one click!
And for dessert – click the extension icon (top-right corner usually) to set a flag that will be added to the ID that you’re copying!

Source code: https://github.com/avi12/steam-id-finder