An audience signal is a suggestion you attach to a Performance Max asset group to tell Google who your likely customers are. It is a starting point for Google’s automation, not a fence. Performance Max can and will show your ads to people outside the signal if it predicts they are likely to convert.
How audience signals work
Each asset group in a Performance Max campaign can carry one signal, built from the same ingredients as ordinary audience segments. The strongest are your own data: past purchasers, website visitors, newsletter subscribers uploaded through Customer Match. Alongside those you can add custom segments based on search terms or competitor websites, in-market and affinity interests, and demographics such as age.
When a new campaign launches, Google has no conversion history to learn from. The signal tells it where to look first. As conversions come in, the system relies more on what it observes and less on what you suggested, and it keeps exploring beyond the signal to find people it did not expect.
Search themes are a separate kind of signal in the same asset group. They describe the searches you want to appear for, rather than the people. The two work together, and neither restricts delivery on its own.
Why it matters
A good signal shortens the learning period. A Performance Max campaign for a London kitchen fitter that starts with a list of past clients and people searching for kitchen renovations will usually find buyers sooner than one that starts with nothing. That matters most on small budgets, where weeks of wasted exploration are a real share of the money.
Understanding that signals are hints also stops you misreading results. If you expected ads to reach only homeowners aged 35 to 64 and the reports show otherwise, the campaign is not broken. That is the design. If you need a hard limit, Performance Max is the wrong tool for that part of the job, though account-level exclusions and brand exclusions can rule some traffic out.
For UK advertisers, the most valuable signals come from first-party data, and that data must be collected and used lawfully. Customer lists need a lawful basis under UK GDPR for advertising use, and website visitor lists only grow from people who accepted advertising cookies.
Common mistakes
- Believing the signal limits who sees the ads, then being surprised by the audience reports.
- Leaving the signal empty on a new account with no conversion history.
- Building a signal from broad affinity interests only and ignoring your own customer data.
- Including existing customers in the signal for a campaign meant to win new ones, without setting the new customer acquisition goal.
- Rebuilding signals every week, which gives the system nothing stable to learn from.
How to act on it
Start each asset group’s signal with your best first-party list: people who bought or enquired. Add a custom segment describing what those people search for, using the terms from your search terms report in other campaigns. Add interests only if they genuinely describe your buyer.
Then leave it alone for several weeks and judge the campaign on conversions and cost per conversion, not on how closely the audience matches your signal. If you want a Performance Max campaign built and checked by someone who will explain each choice, that is part of my Performance Max management.