The Perfectionist project is no longer maintained.
Beautify CSS and SCSS with Perfectionist
Issues with the output should be reported on the Perfectionist issue tracker.
$ apm install perfectionist
Or, Settings → Install → Search for perfectionist
Open the Command Palette and type beautify css or perfectionist.
You can also select some CSS or SCSS in a HTML file and do the above.
There's a Format On Save option and more in the settings.
Set the keyboard shortcut you want in your keymap:
'atom-text-editor':
'cmd-shift-x': 'perfectionist:beautify-css'MIT © Sindre Sorhus