Great question!

The biggest difference, in my opinion, is that Plasmo is a framework, which means you have to learn its abstractions and rely on specific samples tailored for these abstractions to create new extensions. There are config files and specific rules to follow that are not necessarily related to browser extensions.

On the other hand, Extension.js allows developers to create extensions using the standard extension APIs and abstracts only the configuration files, without the need to learn the tooling specifics. This way, a sample from Chrome or MDN that works with a manifest file as the source of truth requires no refactoring to work with Extension.js, making it easier to get started and prototype new projects.

I’ve used Plasmo without touching their framework (essentially using it for HMR and bundling) and it works pretty well

But it’s never a bad thing to have two projects solving a painful problem

Plasmo looks extremely useful. Have you used it to develop any extensions?

I use Plasmo. Strongly recommend it. So much so I gave them a shout-out in a blog post just this Sunday (https://moddable.app/blog/unofficial-mod-support).

I don't really use the framework stuff but HMR that works really well is just chefs kiss.

I use it and it does a lot of what I used to do manual deployment

so I was wondering the same thing as GP, could this be a self-hosted plasmo of sorts