The existence of unblocked versions raises significant intellectual property concerns. Tetris is one of the most litigated properties in gaming history. The Tetris Company, LLC, vigorously protects its trade dress and mechanics.
If you want a safe, verified experience, use the official browser version. It is often unblocked because it is categorized as a legitimate gaming site rather than a "proxy" site. Official Tetris Web Play Tetris tetris 99 unblocked verified