LegendKeeper is a web application you can access from your browser, but you can also use it offline. When you go offline, LegendKeeper holds on to your changes, and will sync them with the server when you go back online.

If you'd like a more app-like experience with LegendKeeper, you can also use it as a "Progressive Web App" if your browser supports it.

For example, in Chrome you can click the "Install" button in your address bar to save LegendKeeper as an app to your desktop.