Prefix Requirements for Key Variables prefix-requirements-for-key-variables

This article describes the prefixes you must attach to key variables when creating trait rules.

Purpose of Key Variable Prefixes

When you create Trait Builder rules, it is important to preface the key variable with a recommended prefix. These prefixes identify the type of data passed in and help avoid namespace conflicts within Audience Manager. Generally, you can give a variable any name, but data for a rule will not process if the key variable name does not match the variable name in an event call.

Prefixes for Key Variables

The following table defines the common prefixes used by Trait Builder.

Key variable prefix
Identifies the variable
As customer specific. This is key data sent in from your own properties.
At the Audience Manager level. This data is uniform across the Audience Manager ecosystem. See Supported Attributes for DCS API Calls for a more complete list.

That contains HTTP header information. Includes header parameters such as referer, IP, accept-language, etc.

Note: For customers using DIL versions older than 9.0, data collection using the h_referer signal will not work on Safari browsers. With the introduction of ITP 2.0, Safari browsers may classify the domain as a tracker and will truncate the referrer on the data collection request to only contain the origin instead of the full URL. See Getting and Implementing DIL Code for the latest DIL version.

Signals using this prefix are not surfaced in Signal Search.


Our Data Collection Servers allow passing of private parameters. Basically, any parameter that starts with p_ will be used for trait evaluation, but it will not be logged downstream, nor stored.

Example: given /event?p_age=23 and a trait like YoungPeople = p_age < 25, the trait will be realized, but the p_age=23 key-value pair will be dropped after the request and will not be logged.