Audience Expansion

Audience Expansion is a campaign setting that automatically widens delivery to members LinkedIn judges similar to your defined audience.

You keep your targeting, but with the toggle on LinkedIn also serves to profiles it considers close matches beyond your exact criteria. It is meant to add reach when a tightly targeted audience is small, and it is a single checkbox at the audience level.

You target a narrow set of job titles at target accounts, the audience is thin, so you enable Audience Expansion and LinkedIn adds adjacent members with similar attributes to keep the campaign delivering.

It quietly loosens the targeting you paid to define. The added members are LinkedIn's guess, not your criteria, and on an account-based campaign that means spending against people outside your list, which defeats the point. Note that this is separate from the retired lookalike audiences; for precise programs, leave Audience Expansion off and widen deliberately instead.

Off by default in your head, whatever the box says.