Eaglercraft 1.21.1: Can You Play the Latest Minecraft Update in Your Browser?
Avoid "No Download" scams: If a site asks you to fill out a survey or download an "unlocker" to play 1.21.1 in your browser, it is likely a scam. The Future of Browser Gaming
Conclusion
5. Known Limitations & Compromises
Because browsers are security-heavy environments, certain vanilla features are altered or missing: