Add Search Themes to PMax Campaigns in Google Ads

Search Themes are signals you provide to Google's AI within a Performance Max asset group to indicate the types of searches you want to target. Unlike keywords, they do not directly control which searches trigger your ads — instead, they inform Google's machine learning about the intent and topics most relevant to your business, helping the algorithm find more of the right customers across all of Google's inventory.

No. Keywords in standard Search campaigns directly control which search queries can match your ads. Search Themes are signals, not hard targeting. They tell Google's AI what themes are important to you, but Google retains discretion on which searches to enter based on its broader optimisation signals. Think of them as guidance rather than constraints — they expand what Google considers relevant for your campaign.

You can add up to 25 Search Themes per asset group. It is generally better to use specific, targeted themes rather than very broad ones. If you have multiple distinct product or service themes, consider splitting them into separate asset groups — each with its own focused set of Search Themes — rather than cramming everything into one asset group.

No — Search Themes are positive signals only. They cannot be used to block unwanted traffic. To exclude irrelevant searches from your Performance Max campaigns, you need to use campaign-level negative keywords, which are managed separately. You can request access to campaign-level negative keywords for PMax through your Google Ads account or Google rep.

Search Themes primarily influence the Search and Shopping inventory within Performance Max. They help Google understand what search intent is relevant to that asset group. For Display, YouTube, and Gmail placements, Google relies more heavily on your audience signals, creative assets, and conversion data rather than Search Themes specifically.

It is recommended to add Search Themes to every asset group, especially when your PMax campaign is new and Google's AI has limited conversion data to learn from. Search Themes help accelerate the learning phase by giving the algorithm clear direction. As the campaign matures and gathers more data, the algorithm becomes less dependent on these signals — but keeping them in place generally maintains better targeting precision.