---
title: "What is a mobile advertising ID (MAID)? | AdBuyMCP"
description: "A resettable identifier assigned by a mobile operating system to a device, used to recognise the same device across apps for advertising."
url: "https://adbuymcp.com/glossary/maid"
---

[Home](https://adbuymcp.com/) / [Glossary](https://adbuymcp.com/glossary) / Mobile advertising ID (MAID)

Targeting and identity

# What is a mobile advertising ID (MAID)?

A resettable identifier assigned by a mobile operating system to a device, used to recognise the same device across apps for advertising. Apple's IDFA and Google's advertising ID are the two that matter.

Also called MAID IDFA GAID advertising identifier

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What it means here

## Here is what the term means for a UK buyer

The definition above holds anywhere. Buying media in the UK adds the detail below, including where AdBuyMCP does something different.

Platform changes have sharply reduced how often these identifiers are available, and the decline runs one way, which is why any measurement spine built on advertising identifiers alone degrades on a schedule somebody else controls. AdBuyMCP holds hashed advertising identifiers for at most 90 days, after which the hash is persistently stripped from the exposure event, re-grading it to a coarser key and keeping the record. That rule lives in the key-translation service, which is the only module we have that performs identity joins at all.

Read next

- [The identity boundary Goes deeper](https://adbuymcp.com/security)
- [The four channels in an awareness plan Channels](https://adbuymcp.com/channels)
- [What UK awareness advertising costs Cost](https://adbuymcp.com/cost)
- [What a fidelity score measures Guide](https://adbuymcp.com/guides/what-a-fidelity-score-is)

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Related terms

## These terms sit next to this one

Most confusion in media buying comes from two adjacent terms being used interchangeably, so these are the neighbours worth reading next.

- ### [Identity resolution](https://adbuymcp.com/glossary#identity-resolution)
  The process of deciding that two different identifiers refer to the same person or household, so that behaviour seen under one can be joined to the other.
- ### [Exposure ledger](https://adbuymcp.com/glossary/exposure-ledger)
  A single record of advertising exposures across every channel, keyed on whichever of four identifiers a channel can supply, with per-key legal grading. They are an opaque household key, a hashed advertising id, a consent-based id and a postcode sector.
- ### [European Unified ID (EUID)](https://adbuymcp.com/glossary#euid)
  A consent-based identifier for European advertising, derived from a hashed email or phone number provided with consent, designed to let first-party audiences be addressed across publishers without third-party cookies.
- ### [Unified ID 2.0 (UID2)](https://adbuymcp.com/glossary#uid2)
  An open-source, consent-based advertising identifier derived from a hashed email or phone number, developed as an industry alternative to third-party cookies. EUID is its European counterpart.

Same group

## These terms are also in Targeting and identity

How an audience is described to a seller, and how much of the description survives. Most media-buying problems start at this translation step.

- [Audience segment](https://adbuymcp.com/glossary/audience-segment)
- [First-party data](https://adbuymcp.com/glossary/first-party-data)
- [Third-party data](https://adbuymcp.com/glossary#third-party-data)
- [Contextual targeting](https://adbuymcp.com/glossary#contextual-targeting)
- [Lookalike audience](https://adbuymcp.com/glossary#lookalike-audience)
- [Retargeting](https://adbuymcp.com/glossary#retargeting)
- [Frequency capping](https://adbuymcp.com/glossary/frequency-capping)
- [Deduplication](https://adbuymcp.com/glossary#deduplication)

[All 81 terms](https://adbuymcp.com/glossary)