Search Themes vs Negative Keywords in Performance Max

Every guide to search themes says the same three things: add up to 25 per asset group, use them for products your landing page does not describe well, treat them like broad match. All true. All incomplete, because none of them says what happens next — that a search theme changes what Performance Max wants to buy, and nothing about what it may buy. Those are two different systems, and advertisers keep using one to try to do the other's job.

What a search theme actually is

A search theme is a phrase you give Performance Max as extra input about what you sell. Google's documentation describes it as a way to tell the campaign about products or services that your website, feed and assets don't already make obvious. It behaves like broad match: Google says search themes match the way broad match keywords do, and that they take priority over the rest of the campaign's automated targeting signals for that asset group.

What it does not do is guarantee anything. You are not buying emergency plumber when you write it as a search theme. You are telling the model "people looking for this are my customers, consider them." The model may serve on that. It may also serve on plumber apprenticeship wage, how to unblock a sink yourself, and plumbers union near me in the same week, because those live in the same semantic neighbourhood and nothing in the campaign said no.

Three practical consequences that the standard write-ups skip:

• Search themes are per asset group, not per campaign. A theme added to your bathroom-fitting asset group shapes that group's targeting. Your negative keywords, by contrast, sit at campaign level and apply to everything under it. The two levers do not even operate at the same altitude.
• Search themes do not have match types. There is no exact-match search theme. There is no way to say "this phrase and nothing looser." Negative keywords do have match types — broad, phrase, exact — and they behave nothing like their positive counterparts, which is its own trap: see negative keyword match types don't work like positives.
• A search theme cannot un-suggest. There is no negative search theme. If the model has decided from your landing page that you serve the recruitment market, you cannot write a theme that says "not recruitment." You can only forbid the terms, one by one, with negatives.

They count against your Search keyword coverage differently than you think

Google states that search themes take priority over other Performance Max signals but that your Search campaign keywords still win when they match a query identically. So an exact-match keyword in your Search campaign still takes the query ahead of a Performance Max search theme. That ordering matters when you run both, but it says nothing about queries neither campaign wants. Those go to whoever is eligible, which is usually Performance Max.

Why adding search themes almost never fixes irrelevant traffic

If you are watching junk search terms roll in and your instinct is to add more precise search themes, the instinct is wrong. You are pouring a suggestion into a system that has already formed an opinion. The junk keeps coming because nothing forbids it.

Here is the shape of it in a real account. A firm sells commercial water filtration systems, average order around $4,000. Performance Max spends $12,000 a month. The search term report shows the campaign paying for water filter cartridge replacement, britta filter jug, water filtration technician jobs and how does reverse osmosis work alongside the handful of terms that actually convert. The owner adds search themes: commercial water filtration system, industrial reverse osmosis unit, water treatment for restaurants. Spend on the junk does not move. Why would it? The themes told the model where to lean. They did not close any doors.

The fix was 40 negative keywords at campaign level, including jobs, salary, career, cartridge, jug, how does as phrase negatives, plus a short list of consumer brand names. That is a forbidding action, and it works the way a lock works — not the way a signpost works.

The general rule: search themes move traffic toward something, negative keywords move traffic away from something. When your problem is "we're not reaching a segment we should," themes are the right tool. When your problem is "we're reaching segments we shouldn't," themes are the wrong tool and always will be. Most Performance Max problems are the second kind. We go through the usual hiding places in where Performance Max wasted spend hides.

The one case where themes reduce waste

There is a partial exception. If a large share of your Performance Max spend is going to a mis-read of what you sell — the model thinks you are a B2C retailer when you are a B2B installer — sharpening the themes across every asset group can shift the centre of gravity enough that some of the bad terms stop appearing. It is slow, it takes weeks of learning, and it is unreliable. You still need the negatives. Think of it as improving the odds, not as a control.

The hard part: Performance Max negatives have real limits

Say the awkward things out loud. Campaign-level negative keywords in Performance Max are the only binding control you get over search terms, and that control has three holes.

No shared lists. A Performance Max campaign does not accept shared negative keyword lists. Your carefully maintained brand-protection list, your job-seeker list, your competitor list — none of them apply. Every negative has to be added to each Performance Max campaign individually. Run six Performance Max campaigns and a single new negative is six additions. Standard Shopping takes shared lists normally, which makes the inconsistency more annoying, not less. We wrote up how Shopping differs in Shopping campaign negative keywords work differently.

The 10,000 cap. A Performance Max campaign accepts up to 10,000 campaign-level negative keywords. That is a lot, and most accounts never approach it, but an account that has been cleaned term-by-term for three years on a broad catalogue can get there. When it fills, you have to prune before you can add, and pruning means deciding which old blocks are still earning their place. Negative keywords in Performance Max and the 10,000 cap walks through what to do as the number climbs.

The report only shows part of the picture. Search terms for Search, Shopping and Performance Max are reported in campaign_search_term_view. Display, Video and App report none. Performance Max serves across all of those surfaces. So the search terms you can see are the Search and Shopping slice of the campaign, and the rest of the spend — the Display placements, the YouTube impressions — produces no search term rows at all and cannot be governed with negative keywords. If your Performance Max campaign is quietly burning money on Display, negatives will not touch it. That is a real limitation and no tool, ours included, works around it. More on what is and isn't visible: Google Ads search terms report, and what it hides.

How to write search themes that don't invite junk

Write themes the way you'd write a shortlist of things you sell, not a shortlist of things people might type. The difference sounds small and produces very different traffic.

A theme like plumbing is an invitation to everything with pipes in it: jobs, courses, DIY guides, supply wholesalers, salary pages. A theme like emergency plumber london same day narrows the neighbourhood the model explores. Neither is a keyword, so neither is precise, but the second one drags fewer strangers in.

Some rules that hold up:

1. Use commercial language, not category language. buy commercial dishwasher behaves better than dishwashers. Intent words in the theme nudge the model toward intent-carrying queries.
2. Do not add themes that duplicate what your landing page already screams. If the page is titled "Emergency Plumber in Leeds — 24/7," a theme saying emergency plumber leeds adds close to nothing. Themes earn their place when they cover something the page does not say — a product line buried three clicks deep, a service you launched last month, a term your customers use that your copywriter doesn't.
3. Keep the count honest. You can add up to 25 per asset group. Adding 25 because the field allows 25 widens the net. Five accurate ones beat 25 approximate ones.
4. One theme, one idea. plumbing and heating and boiler repair and bathroom installation is a theme that means nothing in particular.
5. Write the negatives at the same sitting. When you add the theme water filtration system, you already know that water filtration jobs and water filtration course are coming. Add those negatives before the traffic arrives, not after you have paid for it.

That last point is where most of the value is. Themes and negatives are a pair. Adding one without the other is half a decision. If you are unsure which junk categories will show up, why Google Ads shows irrelevant search terms covers the recurring families — jobs, DIY, free, definitions, competitors, wrong geography.

A workflow that uses both levers in the right order

The order matters because the cheap fix comes first. Do it in this sequence.

Step one: read what you actually bought. Pull campaign_search_term_view for the Performance Max campaign over 60 to 90 days. Sort by cost descending. Ignore conversions for a moment and just read the top 100 terms. You are looking for families, not individual offenders — jobs, salary, free, diy, how to, competitor names, the wrong product category. This is the same discipline as any search term review; how often should you check search terms in Google Ads sets a realistic cadence.

Step two: block the families. Add phrase negatives at campaign level for each family. Phrase is the right default in Performance Max — broad negatives behave unpredictably across match types and will block more than you intended, exact negatives only catch the one spelling. jobs as a phrase negative catches water filtration jobs, jobs in water filtration, water filtration jobs near me and stops there. Be careful with words that read two ways: free blocks free quote, and free quote may be the best-converting term you have.

Step three: measure what you freed up. Not the click count — the money. If the blocked families were costing $1,800 a month out of a $12,000 budget, that is 15% of the campaign now pointed somewhere else. Automated bidding will spend it on the remaining traffic, which is the point. Doing this honestly is harder than it sounds and we argue about the method in how to calculate wasted ad spend honestly.

Step four, and only now: touch the themes. With the bad neighbourhoods fenced off, look at what converted and ask whether any part of your offer is under-represented. If you sell four product lines and three of them never appear in the search terms, that is a signal-coverage problem and search themes are the fix. Add two or three per under-served asset group. Wait two to three weeks. Read the terms again.

Step five: repeat, and prune. Both lists rot. A theme you added for a product you discontinued is still pulling traffic. A negative you added in a panic may be blocking a term that would convert now. Negative keywords hurting performance? Six signs lists the symptoms of over-blocking, which is a genuine risk and not a hypothetical one.

Why the order is not negotiable

If you add themes first, you widen the net before you have fenced anything. The extra traffic lands in the same unfiltered campaign, and you now cannot tell whether a new junk term came from the theme or was always there. Fence first, then widen. It also makes the diagnosis honest: any junk that survives your negatives after a theme change was caused by the theme.

What to do when you run many Performance Max campaigns

The no-shared-lists rule turns maintenance into arithmetic. One negative across eight Performance Max campaigns is eight edits. A 40-term cleanup is 320 edits. Do that weekly by hand and you will stop doing it by the third week — which is exactly what we find in accounts we audit, where the Performance Max negative list was clearly built once at launch and never touched since.

Three ways out, in increasing order of effort saved:

• Editor and bulk uploads. Google Ads Editor handles bulk negative additions across campaigns. It is free and it works. You still have to build the list, and you still have to decide what belongs on it, which is the slow part.
• Scripts. A script can read the search terms and push negatives on a schedule. Someone has to write it, someone has to maintain it when the API changes, and the judgement of which term is genuinely worthless is still yours, encoded as a rule that will be wrong at the edges.
• PPCleaner. We read the search terms your account paid for every night, judge which ones were never going to convert, and add them as campaign-level negatives across Search, Shopping and Performance Max — including to every Performance Max campaign separately, because there is no other way. We never touch budgets, bids, ads or keywords, and we never block a term that converted in the last 90 days. Every block is reversible in one click for 90 days.

What we do not do is write your search themes. That is a positioning decision about what you sell and to whom. It needs someone who knows the business. Blocking a plumber salary query is a mechanical judgement that a machine makes reliably at 3am; deciding that you should be visible for water treatment for breweries is not.

If you are weighing the cost of doing all this yourself against paying someone, the sums are in Google Ads agency or do it yourself. And if you want to see the state of your own Performance Max negatives before anything else, the twenty-minute version is in the Google Ads audit checklist you can run in an hour.

The one-line summary worth remembering

Search themes are what you tell Google about yourself. Negative keywords are what you tell Google about everyone else. When the traffic is wrong, you are almost never suffering from a failure to describe yourself — you are suffering from a failure to exclude. Google's own interface makes themes easy to find and negatives comparatively awkward, and the optimization score will nag you about themes while saying nothing about the terms you are wasting money on. That asymmetry is not an accident, and it is worth resisting.