The Discord Custom Emoji size (128×128px)
Custom emojis are one of the most-used perks of a Discord server, and the recommended upload size is 128x128 pixels in a 1:1 square. Discord accepts larger uploads but downsizes them, and it enforces a small file-size cap, so starting from a clean 128x128 image gives you a sharp result that stays under the limit without heavy compression. Discord then renders the emoji far smaller inline in messages, around 32 to 48 pixels.
The design reality mirrors that tiny render size. Because an emoji appears roughly the size of a line of text in chat, intricate scenes and small lettering turn to mush. The emojis that land are built around one clear idea, a face, a symbol, a reaction, with strong contrast and a readable silhouette. Designing at 128x128 and then previewing it shrunk to about 40 pixels tells you immediately whether the concept survives, and if it does not, simplifying the shape almost always fixes it.
Keeping the image a true 1:1 square avoids Discord padding or distorting it, and a transparent background lets the emoji sit cleanly against both dark and light themes as well as inside reactions. This tool resizes 100% in your browser with no upload, it is free, and it preserves the 1:1 aspect ratio. Discord occasionally changes its emoji size limits, slot counts, and animated-emoji rules, so verify the current requirements before uploading a full set to your server.