Download the HTML file and play even without an internet connection.
The official site provides verified "Offline Clients" that allow you to play without a constant internet connection: EaglercraftX 1.8.8 Offline (JS, zip) : The most stable and widely used version of the game EaglercraftX 1.8.8 Offline (WASM-GC, zip) Eaglercraft 1.8.8 Download Google Drive