Firefox unfortunately does not support the File System Access API. You can try by calling the most fundamental function, the one that asks the user to select a file:

    window.showOpenFilePicker()

What Firefox supports is a "File System API" which creates something similar to the other old ways of storing data in a browser, like cookies and indexeddb. You cannot use it to edit normal files on your disk.

This is my main gripe with Firefox. They force their users to either store everything in the cloud or go through the arcane "download" workflow where you have to manually save files.

> Firefox unfortunately does not support the File System Access API.

I would not call it unfortunate. Browsers should not have access to the file system, USB ports, etc. Perhaps in "PWA"s, if the user has a way of giving and withdrawing consent.

I would prefer that Browsers be given access via permissions - that way webapps will become more prevalent than appstore apps.

Why shouldn’t browsers have these capabilities..?

It's unsafe and allows for even more privacy invasion.

Why is that true? Some applications require file system access. People would grant the application the permission to access files like any other resource like camera, mic, location.

Because vulnerabilities, coarse access granularity and lazy or ill-informed users. E.g., you now grant cam access per domain. Changing functionality on that domain doesn't revoke permission, so a simple bait and switch is already possible. Now imagine granting access to your file system to some Microsoft domain and finding out that there was a change of heart and some new script has uploaded your files to OneDrive and deleted them from your disk.

Taking that logic of protecting users from themselves to the extreme, a website should not be able to display text either. Because it can use text to ask the user to open their explorer and delete the files manually.

I think the flow of Chrome where the user has to select a file from disk and then acknowledge a prompt that the site will have access to that file until they close the window is fine. But if Mozilla wanted to protect users from themselves even more, they could make it as strong as they like. For example, by requiring to turn the functionality on in about:config.

Not giving the user the choice at all, if they want a cloud only browser or a browser that lets them work with local files is the wrong way.