To enable or disable Emmet in a specific language (HTML, CSS, or JSX), go to Editor | Emmet | and toggle the Enable Emmet checkbox. On the Emmet page that opens, choose the key to expand Emmet abbreviations with, by default Tab is selected. Press Ctrl+Alt+S to open IDE settings and select Editor | Emmet.
With WebStorm, you can use native Emmet templates plus more than 200 additional HTML, CSS, and XSL live templates that are listed under the Zen CSS, Zen HTML, and Zen XSL nodes on the Editor | Live Templates page of the IDE settings Ctrl+Alt+S. WebStorm supports such features as new syntax for writing RGBA colors, implied, default, and boolean attributes, the Update Tag action, and more.