A universal ID is a unique identifier that is used to identify and track individuals, devices, or other entities across different platforms, systems, and networks. In the context of advertising and marketing, universal IDs are often used to link and match data from different sources, in order to create a more complete and accurate picture of an individual's interests, behaviors, and preferences. Universal IDs can help advertisers to target and personalize their advertising more effectively, and to improve the performance and measurement of their campaigns. Universal IDs can be created and managed by different organizations, such as publishers, platforms, or data providers, and they can use different technologies and formats, such as cookies, mobile device IDs, or email addresses. Universal IDs can also be subject to different privacy laws and regulations, depending on the location and context in which they are used.