autoprefixer

Prefix CSS and SCSS with Autoprefixer

Install

$ apm install autoprefixer

Or, Settings → Install → Search for autoprefixer

Open the Command Palette and type Autoprefixer: Prefix.
In an HTML file, select the CSS, open the Command Palette, and type Autoprefixer: Prefix.

Open the Command Palette and type Autoprefixer: Remove Prefixes.
In an HTML file, select the CSS, open the Command Palette, and type Autoprefixer: Remove Prefixes.

There's a Run on Save option and more in the settings.

Set the keyboard shortcut you want in your keymap:

'atom-text-editor':
	'cmd-shift-x': 'autoprefixer:prefix'
	'cmd-shift-u': 'autoprefixer:remove-prefixes'