How to unpack .wpress archive files created by the All-in-one-Wp-Migration WordPress plugin

Recently I needed to download some files from a WordPress installation where the client only gave me access to the admin dashboard. Fortunately the All-in-One WP Migration plugin was already installed, so I could take a quick backup of the whole site by downloading the installed plugins, theme and database.

To my surprise downloading the backup from the All-in-One WP Migration plugin only gave me a single compressed migration.wpress file that any unpack tool refused to extract. A little web search brought me to a five year old tool called Wpress-Extractor but the provided binaries for MacOS refused to work because the package was already too old.

So I decided to rewrite this little helpful tool in Node.js to make it cross-platform compatible for Windows, MacOS and Linux.