Use the (still browser-based, just the name) or a trusted 1.17-themed build from a reliable GitHub source.
Some versions allow you to download an HTML file that can be opened in a browser even without an active internet connection. Multiplayer and Customization eaglercraft 1.17 unblocked
: Only use trusted links. Security-conscious users can check for alerts on sites like Virus Bulletin to avoid malicious clones. Use the (still browser-based, just the name) or a trusted 1