User Identifiers | Kevel Audience

User IDs Overview

Each user is associated with a 1st-party identifier, which can be generated either by Kevel Audience or provided by the customer. Additionally, users may have additional identifiers from multiple channels and platforms (e.g., web, mobile apps, CRM systems). By collecting and merging these IDs under a user profile, Kevel Audience enables unified user recognition across channels, allowing for consistent audience segmentation and targeting across platforms.

User Profile Components

A User Profile is composed of:

one or more User IDs that have been explicitly matched together;
a list of User Attributes that is populated by tracking events or offline imports.

Typical HTTP interactions with Audience use a first-party cookie to identify users by default, so no ID needs to be passed explicitly. However, to support cross-channel user identification, additional user IDs must first be matched via ID Matching with the following ID types.

ID Classification

The IDs are classified as follows:

Platform: The platform where the ID is used. Common platforms are browser and mobile. Some IDs are not platform specific, such as the email address, and can be used in any platform.
Channel: The channel from where the ID was generated. For marketing platform IDs, this typically identifies if the ID is 1st or 3rd Party. Specific platform IDs can also exist, such as those from Email or CRM.
ID Type: The identifier to use in ID Matching.
Reliability: Signals whether the ID Type is considered reliable. Unreliable user IDs cannot be used to merge multiple User profiles. Instead, when matching profiles using unreliable IDs, these IDs are simply added to a list of unreliable IDs on the matched user profile. As a result, multiple distinct user profiles may share the same unreliable ID. Although unreliable IDs cannot be used to activate or initiate requests, they can still serve as Activated ID Types in certain Destinations.

Invalid User Identifier Values

The list below outlines invalid user ID values to help avoid common errors in generating or matching user profiles. This results in more accurate attribute building and segmentation:

"" (empty value)
"null" (case insensitive)
"undefined" (case insensitive)
"none" (case insensitive)

Cross-Site or per-Site Profiles

If you operate more than one site, decide up front whether you want a single unified profile per user across all of them, or separate profiles per site. This is a business and privacy decision rather than a technical one.

A single Audience environment can serve more than one first-party domain, but profiles stay separate per first-party cookie unless they are linked through ID matching. Settling this early shapes the domain and tagging strategy.

Default ID Types

Kevel Audience comes pre-configured to accept the following ID types:

ID Types

1st Party Cookie

Platform: Browser
Channel: 1st Party
ID Type: 1pCookie
Reliability: reliable

This ID is automatically generated by Kevel Audience in Web interfaces and is sent via the adstax_uid cookie. It is the default ID type used to identify the user.

Whether that cookie is treated as a genuine first-party cookie by the browser depends on the domain Audience is served from:

Served under your own domain: the adstax_uid cookie is a genuine first-party cookie. It is durable and not restricted by browser privacy settings, so user recognition is reliable.
Served under a Kevel domain: the same cookie is seen by the browser as third-party. Browsers and ad blockers restrict or drop it, so recognition based on it alone is unreliable.

This is the main reason a first-party domain is recommended if you're implementing client-side tracking. See Domain Delegation for setup options and Cross-site User Recognition for how to match profiles across different sources.