It’s a web development pattern so ingrained we barely notice it: hit ⌘-S to save an HTML or CSS file, ⌘-TAB to switch to a browser window, ⌘-R to refresh it, then back to the editor for more changes, repeated dozens of times a day.
Anything that cuts down this series of steps reduces fatigue while forging a closer link between code and design: rather than playing a guessing game (“does this work?” (save / refresh) “maybe this?” (save / refresh)) developers can watch the browser adapt to their code changes in close to real time. There are several tools that accomplish this today, with installation just a click away: