Enhanced (Reach-locked) Lookalike Segments

Audience Studio rolled out an Enhanced Lookalike feature to everyone in phases, started on October 14, 2019 and finished in April 2020.

The Need for a Reach-locked Solution

This enhancement was developed in response to strong customer feedback for a Reach-locked model for better management of campaign media budgets for Lookalike Segments.

Before Enhanced (Reach-locked) Lookalike Segments, the Lookalike Similarity value was locked weekly when the Lookalike models refreshed. Locking the value caused the Reach values to vary. With Enhanced Lookalike Segments, you can input your Reach goal and also choose any Reach value within a given Similarity level. With this release, when the models refresh weekly, Audience Studio returns a Reach value closer to the value that you chose when you created the Lookalike segment. We refer to this experience as ‘Reach-locked’ where previously it was referred to as ‘Similarity-locked’.

Reach-locked Lookalikes

Your Reach is automatically protected and the Segments window no longer displays the Reach Protection button.

In the Segment Summary window, we have removed the curve that depicts the Reach on the X-axis and Similarity on the Y-axis. A more intuitive slider bar replaces the graphs. You can drag the slider bar to any reach value that you wish to lock. You can also enter a reach value in the text box. The Similarity curve appears as a color gradient on the slider bar. The new slider bar displays the similarity level for every reach value, to the right of the bar.


Reach-locked Lookalikes consider the entire available device pool and ALWAYS return the highest (best) similarity of Lookalike devices for the chosen Reach, across the organization.

The Enhanced Lookalikes feature preserves Reach, by allowing Similarity to vary. Similarity is depicted as 3 levels - Strongly Similar, Moderately Similar, and Slightly Similar now instead of a numerical percent value. The similarity levels themselves are inherently stable and do not have to be explicitly locked. For any given Reach value, the possible fluctuation in Similarity across the 3 levels defined is not expected to be as drastic as the Reach fluctuations that were present in the previous experience.

The main impact is that Lookalikes now have very stable populations that do not vary drastically. This means that similarity levels of lookalike segments can vary over time. For example, a segment created in January that is “Strongly Similar” may change and become “Moderately Similar” or even “Slightly Similar” in February. Since we are now defining Similarity in levels as opposed to a single numerical value, we expect these variations to occur infrequently unless there are any significant changes to the 1P universe or 3P data provider taxonomies.

Setting the Reach Values

The minimum reach value that you can select while creating a Lookalike segment is either 0.5% of the model estimated maximum possible reach or 5,000 devices, whichever is greater. This is the value that is shown at the left-most end of the slider bar.

The maximum reach value is determined by the model and is shown next to ‘Estimated Maximum Population’. This is also the value that is shown at the right-most end of the slider bar. This value is your instance’s entire population in the case of Standard Lookalikes or the entire Audience Studio prospecting universe in the case of Prospecting Lookalikes.

Important: We recommended that you DO NOT choose a high Reach value that is close to the estimated maximum population when you create Lookalikes. It will not be possible to guarantee such a reach week over week when the models refresh as there could be changes to Data Providers contributing to prospecting Lookalikes.

When you enter a Reach value that is less than the permitted minimum for the given base segment, or greater than the estimated maximum population, you will see an error message pop up next to the text box asking you to enter a valid Reach size that falls within the permitted range. In addition to the error message, the slider bar and the ‘Create Lookalike’ button will be greyed out - making them unusable.

Lookalikes Modeling

There is no change to the underlying lookalike model, only in the way its outputs are exposed in the product. We now keep the reach value constant and return the best possible similarity for that reach.

There are also no changes to the data providers contributing to Lookalikes or to the way CPM is calculated for billing currently. 

Effect on Previous Segments

Before Enhanced Lookalikes was turned on for your organization, we captured your Reach value as of launch day and locked that value in for every Lookalike segment in the your account. We preserved the Reach size of your existing Lookalike segments. Then these segments were refreshed and the reach preserved, unless there was a change in the overall universe population.

For the segments that were Reach Protected, we captured the existing Reach value (that was protected) in the backend as of launch day, and locked that value in. If the overall population of the entire 1P universe (in the case of Standard Lookalikes) or the 3P universe (in the case of Prospecting Lookalikes) has changed since the segments were Reach Protected and the estimated maximum population for the Lookalike segment is now less than the Reach value that was protected, the entire possible population will be returned for that Lookalike segment when the models refresh, instead of the Reach that was previously protected.

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