Your 'Save' Button Makes Copies. The File System Access API Doesn't.

The classic web 'save' — a Blob and an <a download> link — doesn't overwrite a file, it manufactures a new one every time, leaving notes.md, notes (1).md, notes (2).md scattered in Downloads. The File System Access API fixes this with real, permissioned read-write access to a file on disk. Here's the difference, and why it's Chromium-only progressive enhancement, not a drop-in replacement.