Device.lmt

The operating system's Limit Ad Tracking signal, where 0 means tracking is unrestricted and 1 means the user limited it and tracking must follow the platform's rules. Added in OpenRTB 2.3 and recommended.

CurrentintegerRecommendedSince 2.3

Field facts

Path: device.lmt
Object: Device
Type: integer
Requirement: Recommended
Added: OpenRTB 2.3
Spec section: 3.2.18

How it is used

On iOS, App Tracking Transparency replaced the old Limit Ad Tracking switch, and sellers generally map a missing tracking authorization to 1, which is also when the IDFA comes back zeroed. On Android, deleting the advertising ID or opting out of personalized ads has the same effect. When lmt is 1, buyers should not use the device ID for profiling, retargeting, or cross-app frequency capping. It is a platform signal, separate from legal consent in user.consent or regs.gpp.

Allowed values

0, 1.

Example

Where the field sits in a payload, with everything else left out:

{
  "id": "req-1",
  "device": {
    "lmt": 0
  }
}

Common mistakes

Sending a live device.ifa with lmt set to 1. RTBlint reports that combination as a privacy signal contradiction.
Omitting it on app traffic, which forces buyers to infer the state from whether the ID is zeroed.
Sending true or false instead of 0 or 1.

Version history

Added in OpenRTB 2.3, and present in the latest snapshot. The table shows how each version's spec text types the field.

Versions	Type in the spec	Required	Deprecated
2.3 to 2.3.1	integer	Recommended	No
2.4	integer	Recommended	No
2.5 to 2.6-202606	integer	Recommended	No