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Glossary of Mobile Advertising Terms

UDID (Uniqer User/Device ID)

What is a UDID?

Unique User/Device ID (also known as UDID) is a device or user identifier that consists of numbers and letters, and it’s stored on the mobile device. It’s used to identify every individual smartphone or tablet in the world and it lasts until the device ID is reset (which is very rare) or the account is deleted. It’s worth noting that Device ID is separate from the hardware serial numbers.

What are UDIDs used for?

Its main purpose is to identify the device when installing an app or during registration. For example, apps generally use it as identification when connecting to servers.

In advertising, it’s used by advertisers and marketers to track users and their behavior. Depending on the operating system, there will be some differences. For example, both Google and Apple have their own advertising-specific device IDs.

For iOS, it’s called IDFA (Identity for Advertisers) and for Android, it’s called GAID (Google Advertising ID) or GPS ADID (Google Play Services ID for Android). Device IDs can give an abundance of information that’s crucial for advertising/marketing efforts. If you have the option to track the Device IDs, you can easily see if the users are looking at your ads, installing your apps and so on. "