MakeCode is typically accessed at https://makecode.microbit.org/ where create, modify, and run your projects while you’re online. You can can use MakeCode when you’re offline too. Here are some ways you can work with MakeCode offline:
Offline app

The MakeCode editor is available as app which you can install on a computer with Windows or Mac OS. Once installed, the MakeCode Offline App lets you create, run, and download your projects to the micro:bit. It works the same as the Web application does in your browser but it’s a stand-alone application that will work when a connection to the internet is restricted or not available.