Such a strange comment to read ... quite literally, the reason I first started using Vue over other frameworks was I wanted to put it into legacy apps and did not want to use a build tool. It's one script tag. Not in a half lying way like people say about React, for real. It falls down if you start throwing in components and libraries that presume webpack based setups (which is annoying), but Vue itself is completely and trivially usable with zero build step.