What a mobile advertising ID is
A mobile advertising ID is a string of characters that a phone's own operating system assigns to that device, one per device, not one per person or one per app. On iOS the concept is known as IDFA; on Android it is GAID. Neither is your name, your email, or your account login. It is closer to a serial number that apps and ad platforms can read (with the device's permission) so they can recognize that this is the same phone they saw an ad on before, without knowing who is holding it.
The detail that matters most is that a MAID is resettable and user-controlled. Anyone can open their phone's privacy settings, reset the identifier to a fresh value, or limit apps from reading it at all. Reset it, and every app or ad platform that had it now sees what looks like a new device. That is a deliberate design choice: it gives a person a way to start over, and it means a MAID was never meant to be a permanent fingerprint. For more of the vocabulary around measurement, the DOOH glossary defines the surrounding terms in one place.
How a MAID is used in advertising measurement
In ordinary app and web advertising, a mobile measurement partner sits between an ad platform and an app. When someone sees or taps an ad inside an app, that ad platform can log the MAID alongside the event. If that same device later opens the advertised app and, say, completes a purchase, the app can log the same MAID against that action. The measurement partner matches the two records and credits the earlier ad with the later result. It is how a marketer sees which ad led to which install without either side handing over anyone's name.
That match is never total. If a person reset their MAID between the ad and the purchase, or never allowed the app to read it in the first place, the link cannot be made and that action goes unmatched. Companies that do this kind of measurement report it as a partial, best-effort picture built from the devices that could be matched, not a complete count of everyone who saw an ad. That honesty about the gap is part of how the whole approach is meant to work under consent.
How this relates to DOOH measurement
An out-of-home screen has no login and no click, so on its own it cannot see a MAID. What some measurement partners do instead is compare a device's location data, gathered with consent through the apps that device already uses, against where and when a DOOH campaign ran, then use a MAID logged by an app to connect a person who was likely near a screen to a later visit or purchase on their phone. It is one extra layer added on top of a campaign, not a replacement for it. The billboard attribution guide walks through real cost-per-action numbers gathered this way, and the wider measurement topic hub covers the rest of the vocabulary.
On Blindspot, that measurement layer stays separate from the price. Every screen on the map still prices and bills per play, whether or not a brand ever adds a measurement partner on top.
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screens priced per play, MAID or not
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countries, one pricing unit
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from, average cost per play
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self-serve booking starts from
Building the plan itself does not require touching any of this. Blinky, the free planner, turns a plain-English brief into a schedule of screens and hours, priced per play from the start. See the full breakdown in the DOOH price index or the billboard cost guide, both priced the same way regardless of what a brand's measurement partner can later match.
A MAID measures what happens after a play, not the play itself.
The distinction, in one line