You need the correct launcher/site. Do not use the newer "EaglercraftX" sites.
The Ultimate Guide to Eaglercraft 1.5.2 Server IPs: How to Play Minecraft in Your Browser Eaglercraft Server Ip 1.5.2
Go to Options > Video Settings . Turn down your Render Distance to 4 or 6 chunks, set Graphics to "Fast", and turn off Smooth Lighting. You need the correct launcher/site
A step-by-step guide to making an EaglercraftX server! * Go to any hosting provider, such as aternos or magmanode, and make a 1.8. set Graphics to "Fast"