Many versions allow you to export your world as a file, ensuring you don't lose progress when clearing your browser cache. How to Access and Play
You can often find an index.html file that allows you to play the game even without an active internet connection.
To get the most out of your 1.15 session, consider these adjustments:
Since it runs on JavaScript and HTML5, you only need a browser like Chrome, Firefox, or Edge.
Many developers host "unblocked" mirrors on Github.