minecraft-bedrock-json-schemas/source/general/block/identifier.json

{
  "$id": "blockception.minecraft.block.identifier",
  "description": "A minecraft block identifier",
  "examples": ["namespace:block"],
  "pattern": "^[0-9a-zA-Z:_\\.\\-]+$",
  "title": "Block Identifier",
  "type": "string"
}