If the unblocked browser versions are laggy or restricted, consider these alternatives:

It runs directly in the browser, so you don't need to download any files or install anything on the computer. It’s a great way to experience the base game if you can't access Steam.

For many students and office workers, gaming sites are often restricted. Unblocked Games 66 is a popular proxy site that hosts a massive library of flash and HTML5 games, including The Binding of Isaac .