PMax search themes: steering without keyword lists in 2026

Performance Max has matured into one of the most powerful campaign types in Google Ads, but a fundamental question persists for many advertisers: how do you steer a campaign that largely decides for itself where it appears? In 2026, Google's primary answer to that question is search themes. Search themes are directional signals you add to a Performance Max campaign to tell Google AI which search intents are relevant to your business. No keyword lists with match types, no separate ad groups per search term, but a direct instruction to the underlying model: these are the topics that matter for my offering. This article explains what search themes are, when they work best, how to configure them effectively, and how AdBrains AI technology takes this steering mechanism to a structurally higher level.

What are PMax search themes exactly?

Search themes vs. traditional keywords

How the two approaches compare within Performance Max

Traditional keyword lists

• Manual maintenance and expansion
• Fixed match types (broad/phrase/exact)
• Separate campaign per intent cluster
• Negative keywords added manually
• Limited cross-channel reach
• High maintenance load per account

PMax search themesRecommended for PMax

• Google AI steers on intent, not text
• No match types, directional signal only
• One campaign, all channels at once
• Negative keywords still possible
• Seamless channel mix per auction
• Low maintenance, high coverage

Search themes are short text phrases, similar to keywords but without a match type, that you add to an asset group within a Performance Max campaign. They tell Google AI which search queries are relevant to your offering without locking Google into exact text variations. Google uses the search themes as one of many signals when evaluating whether an auction is relevant to your campaign. Other signals include landing page content, ad assets, audience signals, and historical conversion data.

The most important distinction from traditional keywords is the nature of the signal. Where an exact match keyword like [electric folding bike buy] instructs Google to bid only on that precise query, a search theme such as "buy electric folding bike" gives Google the freedom to also consider semantically related queries. Search themes are therefore broader than exact match but more targeted than broad match keywords in regular Search campaigns. They sit at the intersection of control and scale.

You can add up to 25 search themes per asset group. Google advises keeping them specific so they genuinely add value beyond what the AI already detects via assets and landing pages. A too-general theme like "bicycles" adds little if the rest of your campaign is already full of relevant content about electric bikes. A specific theme like "foldable e-bike for daily commuting" gives Google a clear signal that this intent segment deserves priority.

When are search themes most effective?

Search themes are not equally valuable in every situation. They deliver the most impact under the following circumstances:

• New products or niches with limited historical data: when Google has few conversion signals for a product, search themes help guide the AI in the right direction from day one.
• Seasonal campaigns: during temporary promotions or seasonal peaks, you want to act quickly without building an entire keyword structure. Search themes provide immediate steering.
• Expansion into new market segments: when an existing brand launches a new product type, a dedicated asset group with specific search themes quickly orients the AI toward the new segment.
• Accounts with limited search volume data: smaller advertisers with little historical data benefit from search themes as a clear directional signal for the AI.
• Campaigns without hard exclusions: when you deliberately give Google AI room to discover, but want to ensure the core of the search intent spectrum stays on target.

For a client like E-4motion.com, which sells new electric folding bikes, search themes are particularly well suited. The target audience searches across widely varying queries: from "compact e-bike for train commuters" to "foldable bike with battery for daily use." A broad keyword strategy risks fragmentation or missing semantically related but converting queries. Search themes provide the balance: you give Google direction on relevant intent clusters without having to define every variant individually.

How to configure search themes effectively

An effective search theme configuration follows a set of clear principles. The first step is inventorying the intent clusters relevant to your product or service. These are not random keywords but groups of similar search intents, which you then translate into one or more representative theme phrases.

Consider Clima-Active.nl, a company offering air conditioning and heat pump installations operating in the lead generation market. For a PMax campaign targeting quote requests, you might set the following search themes:

• "air conditioning installation quote request"
• "heat pump installation cost estimate"
• "combined cooling and heating solution home"
• "energy-efficient air conditioning residential"
• "heat pump subsidy application 2026"

Notice the specificity levels. Each theme targets a different intent layer: the first is directly transactional, the second is cost-oriented, the third focuses on use case, the fourth on sustainability considerations, and the fifth on current regulations. Together they give Google a broad but relevant framework to evaluate auctions without requiring management of hundreds of individual keywords.

Average performance improvement with search themes

Benchmarks for advertisers actively using PMax search themes (2026)

More tracked conversions

27%

Higher Ad Strength score

34%

Lower CPA vs. no steering

19%

Better ROAS vs. no steering

22%

More relevant impressions

41%

A second principle is consistency with the rest of the asset group. Search themes that do not align with ad assets or landing page content create confusion in the AI. If all assets focus on air conditioning installation but you add a search theme about solar panels, that creates conflicting signals. Google will not serve that theme efficiently because landing page relevance is absent.

The third principle is regular evaluation. Search themes are not a set-and-forget configuration. Through the search terms report in Google Ads, you can review which queries trigger your PMax campaign and assess whether the themes are activating the intended intent clusters. If you see many irrelevant queries, it is time to refine the themes or add negative keywords at the account level.

Search themes and their relationship with other campaign types

A frequently asked question is how search themes relate to existing Search campaigns in the same account. Google follows a prioritization order in which exact match and phrase match keywords in regular Search campaigns take precedence over PMax search themes for identical or very similar queries. This is a deliberate choice to give advertisers the control they expect for their highest-value keywords.

In practice, this means PMax search themes are best used to expand your reach, not to replace your most valuable exact keyword campaigns. For ToetsJeKennis.nl, a platform for online exams and courses, you would manage the exact keywords for the most popular exam titles in a dedicated Search campaign. The PMax campaign with search themes then captures the broader exploratory queries, such as "online certification course" or "accredited business training exams," which are difficult to capture in a tight keyword structure.

The table illustrates that PMax with search themes offers the best balance between scale and relevance control for advertisers who do not want to manage every keyword manually but still want influence over the intent coverage of their campaigns.

How AdBrains AI automates search theme steering

At AdBrains, we have built our own AI technology to fully leverage the potential of PMax search themes. While most advertisers configure search themes based on intuition or a one-time keyword analysis, our system operates continuously and data-driven.

Our automated search term mining system analyzes all incoming queries at the campaign level every single day. It not only detects which terms convert, but also which intent clusters are underrepresented in the current search theme configuration. When the AI identifies that a new semantic cluster of queries consistently delivers high conversion value but is not covered by existing themes, it automatically generates a proposal for a new search theme. That proposal is then reviewed by our multi-agent verification system: four independent AI agents assess relevance, overlap with existing campaigns, and cannibalization risk before the theme is implemented.

AdBrains also applies the Keyword Incubator methodology to search themes. New theme candidates are first tested in a shielded incubator campaign, where the AI measures performance without risking the production status of existing campaigns. Only when a theme has generated sufficient conversion signals is it promoted to the production campaign. This significantly shortens the learning phase of PMax campaigns and reduces the risk of budget waste during ramp-up.

For e-commerce clients like E-4motion.com, our system links search theme optimization directly to Target ROAS targets. If the ROAS of a specific intent cluster drops below the threshold, the AI triggers a review of the related themes and assets, resetting the steering focus. Simultaneously, our strategy-switch system monitors whether the campaign has enough conversion signals for Smart Bidding to work effectively. If conversion volume is too low, the system automatically shifts to a more conservative bidding target until the data foundation is sufficient again.

For lead generation clients like Clima-Active.nl, the system operates the same way but targets are driven by Target CPA instead of Target ROAS. The AI continuously monitors the quality of incoming leads per intent cluster and adjusts search themes when a cluster structurally delivers lower-quality leads. This keeps the campaign efficient not just in cost, but also in lead quality, which is exactly the kind of nuance that manual management cannot consistently deliver across dozens or hundreds of theme variations simultaneously.

Finally, our server-side signal enrichment enriches the conversion signals PMax needs for effective Smart Bidding. Through our own sGTM infrastructure, we feed first-party conversion data back to Google, allowing the model to more accurately learn which search intents generate genuinely valuable customers. Combined with well-configured search themes, this means the AI learns faster and more reliably, translating into better campaign performance from an earlier stage.

PMax search theme funnel

From search query to conversion via search theme steering (percent-mode)

Relevant queries reached

Search themes guide Google AI at intent level

Ad clicks

Average CTR with well-configured themes

Landing page visitors

After quality and relevance filter step

Conversions achieved

E-commerce benchmark with tROAS steering

Average industry benchmark for PMax e-commerce in 2026

Common mistakes when setting up search themes

Even with a powerful tool like search themes, things regularly go wrong in practice. The most common mistakes include:

• Too broad or generic themes: themes like "shoes" or "insurance" are so broad they provide no meaningful steering. Google AI already knows your website is about shoes from the assets without your instruction.
• Inconsistency with assets: themes that do not align with ad copy or landing page content lead to lower Ad Strength scores and confusion in the model.
• No negative keywords added: search themes are not a guarantee against irrelevant traffic. Without account-level negative keywords, PMax can still appear on unwanted queries.
• Never revisiting themes: market conditions and search intents change. Themes that were relevant six months ago may now be outdated or less effective.
• Ignoring overlap with existing Search campaigns: if search themes overlap with exact match keywords in a separate Search campaign, this can lead to internal competition and higher costs.

FAQ: PMax search themes

What is the difference between a search theme and a keyword in Google Ads?

A keyword is an exact or partially exact instruction to Google to appear for specific search terms, depending on the match type. A search theme is a directive that tells Google AI which intent your campaign is relevant for, without a hard link to specific text variations. Search themes are therefore more flexible but less predictable in terms of exact query triggers. They are designed for use within Performance Max campaigns and work through the overarching Google AI model that weighs all campaign signals together.

How many search themes can I add per asset group?

Google allows a maximum of 25 search themes per asset group. In practice, most experts and AdBrains recommend starting with 5 to 10 well-supported themes per asset group. More themes do not automatically mean better performance. The risk of signal dilution increases if themes are too diverse or generic. Choose fewer, more specific themes that together form a coherent intent cluster rather than a long list of loose terms.

Do search themes also influence channels other than Search?

Search themes are primarily designed as steering signals for search network auctions within Performance Max campaigns. On visual channels like YouTube, Display, or Discovery, the AI steers on audience signals, assets, and contextual targeting. Search themes have an indirect influence on those channels through the overarching campaign model, but they are not a direct steering mechanism for non-search inventory.

Can I combine search themes with audience signals in the same asset group?

Yes, and it is actively recommended. Search themes and audience signals are complementary steering instruments within a Performance Max asset group. Search themes give direction on what people are searching for, while audience signals give direction on who the most valuable users are. Combining both provides Google AI with a richer signal landscape from which to learn, positively affecting campaign convergence speed. At AdBrains, our audience management automation system maintains PROD, Incubator, and RLSA audiences on a weekly basis, ensuring audience signals are always current and work optimally alongside search themes.