Search Themes in Performance Max: How to Steer the AI Toward the Right Customers
9 min read · AstraLoop Studio
Performance Max has a flaw everyone knows about and few know how to manage: it's an almost-closed box. You give Google a budget, a goal, and some assets, and the algorithm decides on its own which searches, which audiences, and which networks to spend on. It works well when you have abundant data and clean conversions. It works much less well when you're starting from zero, running lead generation for a niche service, or when the AI, left to its own devices, starts sending you leads that have nothing to do with what you sell.
Search themes are the lever designed for exactly this problem. They don't hand you back full control — in Performance Max, that's gone for good — but they let you tell the algorithm: "look, the customers I want search for things like this." It's a directional signal, not a command. Understanding that difference changes everything.
In this guide we'll look at what search themes really are, how to add them without shutting off automation, and how to use them in a concrete B2B lead generation case. No abstract theory: real examples, real limits, and an operational checklist.
What search themes are (and what they're not)
Search themes are phrases or keywords you add at the asset group level inside a Performance Max campaign. They tell Google what kinds of searches you associate with your ideal customers, especially when the campaign is new and hasn't yet gathered enough data to figure that out on its own.
The single most important thing to grasp is this: a search theme is not an exact-match keyword. In a traditional Search campaign, an exact-match keyword tells you precisely which queries you'll show up on. A search theme, by contrast, is a probabilistic input. Google treats it as one of many signals for steering automation, alongside account history, assets, audience signals, and conversion data. It can surface on searches related to what you specified, but with no hard guarantee.
Google itself describes it as equivalent, in priority terms, to a broad-match keyword. That has two practical consequences.
- They inherit broad-match behavior. Wide-reaching, exploratory, capable of catching related intent you hadn't anticipated. Great for uncovering demand, risky if you don't keep it in check.
- Account-level negative keywords take precedence. If you have a negative keyword at the account level that conflicts with a search theme, the negative wins. It's your main safety brake.
You can add up to 25 search themes per asset group. You don't need to hit 25: a handful of sharp, coherent themes beats a sprawling, confusing list that ends up sending the algorithm contradictory signals.
Why they actually matter, in practice
If you leave Performance Max completely free at launch, the algorithm explores. And exploring costs money: it means showing your ads to audiences that might convert, testing hypotheses with your budget. Given enough budget and enough time, it converges. But if your budget is limited or your conversion cycle is long (typical in B2B), you risk burning the first few weeks on the wrong traffic before the AI even figures out who you're after.
Search themes shorten that learning phase. They give the algorithm an informed starting point instead of letting it start blind. That's not a minor detail: in Google Ads lead generation, the quality of the first conversion signals decides which direction the AI will optimize toward for weeks.
Search themes vs. keywords: when to use which
The question comes up often: if I want control over the searches I appear on, wouldn't a regular Search campaign be better? It depends on the goal. Here's a practical comparison.
| Aspect | Keyword (Search) | Search theme (PMax) |
|---|---|---|
| Control over queries | High (especially with exact match) | Low, it's a directional signal |
| Networks covered | Search network only | Search, Shopping, Display, YouTube, Gmail, Discover, Maps |
| Behavior | Defined by match type | Similar to broad match, exploratory |
| Priority in a conflict | Exact-match keywords in the account take precedence over PMax | Yields to the account's negatives and exact matches |
| Best for | Warm demand, clear intent, control over cost per click | Scaling, covering every network, giving the AI direction |
One useful technical point: if the same account has a Search campaign with an exact-match keyword identical to the query, that campaign takes precedence over Performance Max. It's a way to shield your most valuable searches (typically your brand) from PMax and let the two logics coexist instead of competing. If you want to dig deeper into choosing between the two approaches, we have a dedicated guide on Performance Max vs. Search, which one to choose.
Use case: B2B lead generation on a tight budget
Let's see how all of this applies to a real scenario. Picture a company selling accounting software for bookkeeping firms. Goal: generate qualified demo requests. Modest starting budget, long sales cycle, very specific target. The worst-case scenario for letting PMax run blind.
Step 1. Define the themes from the customer's own language
The best search themes don't come out of an internal brainstorm; they come from how your customers describe the problem. For our bookkeeping firm, the themes might be:
- accounting software for bookkeeping firms
- e-invoicing software for accountants
- practice management software for professional firms
- tax deadline tracking software
Notice the level of intent: these are searches from people who already have the problem and are looking for a solution, not idle curiosity. Avoid overly broad themes like "accounting software" or "bookkeeping": they'd bring in wide, poorly qualified traffic — exactly what the AI would amplify. If you know how to map your customers' needs, generating qualified leads starts right here, by capturing the right intent before you even write the ad.
Step 2. Build the negative-keyword shield
This step is non-negotiable. Since search themes behave like broad match, without negatives they'll pull in tangential traffic. For our example, negatives at the account or campaign level:
- free, gratis, no-cost (people searching for free aren't buying paid software)
- course, tutorial, jobs, job openings (learning or job-hunting intent, not buying intent)
- excel, template, free template (DIY intent, not ready to buy)
Remember: account-level negatives beat search themes. They're your primary tool for keeping the flow clean. It's worth building a structured list from day one; our guide on negative keywords in Google Ads explains how to set it up without leaving gaps. And if junk leads are your main problem, there's a dedicated deep dive on how to stop junk leads.
Step 3. Feed the AI the right data
Search themes give direction, but the algorithm optimizes on conversion signals. If you count every form submission as a conversion, PMax will learn to bring you volume, not quality. This is the most common mistake in B2B.
The fix is to feed Google the real quality of the lead, not just the volume. That means passing offline conversions from your CRM into the campaign: not just "form submitted," but "lead became a qualified demo" or "lead became a customer," with the corresponding value. That way the AI optimizes toward people who resemble your real customers, not the merely curious. This is the real multiplier: search themes for direction, offline conversions for quality. On their own, themes point the way; combined with CRM data, they become a machine that learns who's actually worth pursuing.
Want to set up Performance Max so it brings in qualified leads instead of junk contacts? Request an audit of your account: we'll look at themes, negatives, and tracking together.
Step 4. Read the reports and correct course
Performance Max has gotten better on transparency since its early days, but it's still more opaque than Search. After a few weeks of data, check:
- Search terms report (at the campaign level): shows which categories of queries you're showing up on. Use it to spot tangential themes to block with new negatives.
- Audience insights: who's actually converting, so you can adjust your themes toward the right segments.
- Performance by asset group: if a group with certain themes is performing much better, that's your cue to shift weight toward it.
The work doesn't end at launch. Search themes need revisiting as the data comes in: add the ones that work, drop the ones bringing in the wrong traffic, reinforce your negatives. It's maintenance, not set-and-forget.
The mistakes we see most often
In our audits of accounts running Performance Max, the same problems keep coming up. Worth listing them, because every one of them is avoidable.
- Themes that are too generic. "Shoes," "software," "consulting" give no direction: they tell the AI to explore an ocean. The more specific the theme is about intent, the better it guides.
- No negative-keyword list. Search themes without negatives is like turning on the tap without knowing where the water ends up. Tangential traffic costs you money and doesn't convert.
- Confusing volume with quality. Optimizing on "form submitted" instead of the lead's real value is, in B2B, the fastest way to fill your CRM with useless contacts.
- Changing everything every three days. PMax has a learning phase. Constant edits reset it. Give it at least two weeks of data before stepping in, then adjust with judgment.
- Ignoring brand exclusion. Without excluding branded traffic, PMax often takes credit for conversions you would have gotten anyway, inflating your numbers. See how to handle it in excluding brand from Performance Max.
The common thread across all of these mistakes is one thing: treating Performance Max as if it were magic or, conversely, as if it were Search in disguise. It's neither. It's an automation system that performs well only if you feed it quality inputs and keep governing it consistently. Search themes are one of those inputs — among the most important at launch.
How this all fits into your Google Ads strategy
Search themes aren't a standalone tactic; they're one piece. They work if the rest of the setup is in order: the right conversion goal, reliable tracking, CRM data flowing back into the campaign, well-maintained negatives. Miss one of those pieces, and themes alone won't be enough.
That's why we always place them inside a broader framework. If you're setting up Performance Max from scratch, start with our complete guide to Performance Max. And if you want to understand how Google Ads fits into your customer acquisition system, instead of remaining an island disconnected from the rest, the deep dive on integrating your CRM and sales funnel closes the loop: the leads coming in through search themes need to land in a process that qualifies and converts them, not a forgotten spreadsheet.
Put simply: search themes give you the direction, tracking tells you whether it's the right one, and the CRM closes the loop by teaching the AI who's actually worth it. Three pieces, one system.
Frequently asked questions
What's the difference between search themes and keywords in Performance Max?
Keywords (in Search campaigns) give you direct control over which queries you appear on, especially with exact match. Search themes are a directional signal that steers PMax's automation and behave like broad match: more exploratory, with no hard guarantee on which searches they'll cover.
How many search themes can I add to a Performance Max campaign?
You can add up to 25 search themes per asset group. It's better not to fill all of them: a handful of coherent, intent-specific themes guide the algorithm better than a long, confusing list that ends up sending contradictory signals.
Do search themes ignore my negative keywords?
No, it's the opposite: account-level negative keywords take precedence over search themes. They're your primary tool for keeping traffic clean and preventing themes — which behave like broad match — from pulling in tangential searches that don't convert.
Are search themes useful only at launch, or for an already-running campaign too?
They're most useful at launch, when the campaign doesn't yet have enough data to figure out on its own who you're after. As conversions accumulate, their relative weight decreases, but they remain useful for providing direction, correcting drift, and covering new intent segments.
Do search themes improve lead quality on their own?
On their own, they only provide direction. Real quality comes when you combine them with offline conversions from your CRM: that way the AI optimizes toward people who resemble your real customers, not the merely curious. Search themes for direction, CRM data for teaching the algorithm what's actually worth it.
Is Performance Max with search themes better than a classic Search campaign?
It depends on the goal. Search gives you fine control over queries and cost per click and is ideal for warm demand. PMax with search themes covers every Google network and scales better. Often they coexist: Search guards the brand and your most valuable searches, PMax scales the rest.
If Google Ads is bringing you volume but few real customers, let's talk: we connect campaigns, CRM, and offline conversions so the AI learns who's actually worth it.