IconVault's File System Access playground uses the real picker APIs: open a text file from your disk, edit it in the live editor, and save straight back to the same file with no download step. You can also Save As, start a new file, and browse a whole directory with names, kinds and sizes. It is free and runs fully in your browser.

You will learn how file handles persist user permission across the session, the difference between reading with getFile() and writing with createWritable(), and why every access starts with an explicit picker gesture. Nothing is uploaded: the browser mediates a local file reference, and the permission badge shows exactly what access was granted.