You need the actual browser client file. One reliable source is the official Eaglercraft repository or one of its many mirrors. Several community members have published HTML files for versions 1.5.2 and 1.8.8.
Its primary audience is students trapped behind school firewalls, players on Chromebooks, or anyone who wants to play Minecraft on a locked-down machine. eaglercraft 2b2t
For the uninitiated, Eaglercraft is a remarkable piece of reverse engineering. It allows players to run Minecraft 1.5.2 (or similar versions) directly inside a web browser using WebAssembly and HTML5. It bypasses the official launcher, uses its own skin system, and crucially, does not require a premium Mojang account. You need the actual browser client file
The real 2b2t players use mods like Impact, Future, or Rusherhack. You are in a browser. You have zero hacks natively. You will die instantly unless you prepare. Its primary audience is students trapped behind school