When creating your very own custom Add-On for Minecraft Bedrock Edition, you will need to generate a UUID. This is a Univerally Unique Identifier. Basically, it is like the barcode for your product. It can't be the same as anyone else's. Don't manually create a UUID...that is dangerous. There are UUID generators built-in to many code editors if you are ambitious enough to get that configured. If not, there's a useful web site that will generate a UUID for you every time you reload the page.

Need a UUID? Try this online UUID generator: