Device.language

The browser or device language as a two-letter ISO 639-1 code, such as "en" or "de". Present since OpenRTB 2.0.

CurrentstringOptionalSince 2.0

Field facts

Path: device.language
Object: Device
Type: string
Requirement: Optional
Added: OpenRTB 2.0
Spec section: 3.2.18

How it is used

Use lowercase two-letter codes only. A tag that includes a region or script, such as "en-US", belongs in device.langb, and only one of the two should be present.

Example

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

{
  "id": "req-1",
  "device": {
    "language": "en"
  }
}

Common mistakes

Sending a locale such as "en-US" or "en_US" here. Those are not ISO 639-1 codes.
Sending both language and langb, which the validator reports as mutually exclusive.

Version history

Added in OpenRTB 2.0, 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
2.0 to 2.2	string	No	No
2.3 to 2.3.1	string	No	No
2.4	string	No	No
2.5 to 2.6-202606	string	No	No