Roblox is not a browser game in the traditional sense. When a user clicks "Play" on the official Roblox website, it launches a protocol that opens a separate, heavy-duty executable application (the Roblox Player). This application requires installation, utilizes 3D hardware acceleration, and consumes significant bandwidth. These characteristics make it easy for firewalls to detect and block.
Many games hosted on unblocked sites are not created by the official Roblox Corporation. They are "clones" or fan-made replicas. While many are harmless, the quality control is non-existent. Some may contain buggy code or, in rare worst-case scenarios, malicious scripts hidden within the game files. ubg365.github.io roblox