I have a problem with jinja2 highlighter in sublime 3.All the files associated with .html extensions don't recognize jinja templates blocks..I searched the web but the only solution I found is to make a .jinja.html custom extension..anyone got any idea how to solve this?..This is the plugin I installed https://packagecontrol.io/packages/Jinja2
You need to add .j2 to your file extension:
mysupertemplate.html.j2
Have a look at the syntax file (under fileTypes)