Sublime Snippet Not Working

Sublime 3 needs snippets to have .sublime-snippet endings in file name.

You should use text.html instead of source.html in scope block.

You should escape dollar signs in your snippet. $ -> \$.

Step1. For html snippet, please change

<scope>source.html</scope>

to

<scope>text.html</scope>

Step2. If you want sublime to show tooltips after you input the keywords, add this line

"auto_complete_selector": true

to your Preferences - Settings User file