The worlds are saved as part of your browser's nearby storage, you'll be able to export them as EPK information and import them once more on all other Eaglercraft web sites that also help singleplayer. I'd an old Mate his username was d4vd. He later switched his title to https://www.reddit.com/user/ukIsmine/comments/11suiwb/a_comprehensive_guide_to_eaglercraft_minecraft/