def is_valid_mojang_uuid(uuid):
    """https://minecraft-de.gamepedia.com/UUID"""
    allowed_chars = '0123456789abcdef'
    allowed_len = 32
    uuid = uuid.lower()
    if len(uuid) != 32:
        return False
    for char in uuid:
        if char not in allowed_chars:
            return False
    return True
