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On macOS, use ⌘ in place of Ctrl and ⌥ in place of Alt — the in-app list adapts automatically. Every shortcut also has a menu or toolbar equivalent, so the editor is fully usable on a phone or tablet with no keyboard.
Everything you type is written to this browser's local storage every 500ms and restored when you come back. Nothing is sent anywhere — there is no server behind this page and no account to create. The trade-off is that your notes are tied to this browser on this device: clearing your browsing data deletes them, and there is no copy for us to restore.
Install it from your browser's address bar to keep working with no connection, and use File → Export to take a note somewhere else as .txt, HTML, PDF, or Word.