Earlier quoted context omitted.
Here, let me do the equivilant of LMGTFY: https://github.com/bertfreudenberg/SqueakJS/search?utf8=%E2%... Looks like it's storing settings, images, and files created by said images. Reminder that Squeak is a full VM and naturally has file-io abstractions which must be implemented.
Right, brainfart and I couldn't remember the name of that API. Thanks!
Large data (file contents) is stored in IndexedDB, only settings and file meta data in localStorage.