Negative Keywords and Search Themes in a PMax World
How negative keyword lists and PMax search themes work together to keep Shopify ad spend focused on qualified traffic.
Written by Mantas Jurgutis — Founder, Adsify — builds the Google & Meta automation merchants use daily
Editorially reviewed by Adsify Editorial on March 7, 2026 — Reviewed against Shopify, Google Ads and Meta official documentation.
Two different tools solving overlapping problems
Negative keywords and PMax search themes look similar on the surface — both involve typing phrases related to your products into a campaign settings screen — but they do fundamentally different jobs. Negative keywords actively block your ads from showing for matching queries in Search and Shopping campaigns. Search themes are a positive signal fed to PMax's automated system, suggesting the kinds of queries an asset group should try to match, without guaranteeing exclusivity or exclusion of anything else. Understanding that difference changes how you should be building both lists inside a Shopify advertiser's account.
Where negative keywords still apply directly
Standard Search and Shopping campaigns support negative keywords at the campaign or ad group level, added under Keywords > Negative keywords in the left navigation. If you run a supplementary Search campaign alongside PMax (covered in the campaign-type comparison in our related article), negative keywords remain your primary lever for excluding irrelevant traffic — terms indicating research intent without purchase intent ('how to', 'DIY', 'free'), competitor brand names you don't want to piggyback on, or category-adjacent terms for products you don't actually sell.
PMax's account-level negative keyword exception
Performance Max historically didn't support negative keywords at all, which frustrated advertisers trying to exclude brand-damaging or irrelevant placements. Google has since allowed account-level negative keyword lists to apply to PMax campaigns through a support request process, documented in support.google.com/google-ads — this is more restrictive than campaign-level negatives in standard Search and is intended for brand safety exclusions rather than routine keyword hygiene, so it shouldn't be treated as a substitute for well-built search themes.
Why search themes aren't a suppression tool
A common misconception is that omitting a topic from search themes will prevent PMax from matching it. It won't. PMax pulls signals from your product feed, landing pages, audience signals, and search themes together, and can still match queries outside your explicit search themes if the broader system believes they're relevant. If a category of traffic is genuinely unwanted — say, a wholesale-only SKU line you don't want retail traffic reaching — that requires an account-level negative keyword request or, more simply, keeping that product out of the feed segment PMax's asset group draws from.
Structuring search themes around real search intent
Effective search themes read like the transactional keyword phrases a customer would actually type, not category labels. 'Women's waterproof hiking boots' is a usable search theme; 'footwear' is too broad to give the system meaningful direction. Add search themes under each asset group's Audience signals section, ideally sourced from the same Keyword Planner research used elsewhere in your account, and limit each asset group to a tight, coherent product category so the search themes, images, and headlines all reinforce the same intent rather than spreading across unrelated products.
Auditing what PMax is actually matching
Because PMax doesn't expose raw search query text the way Search campaigns do, the closest visibility you get is the 'Search categories' report inside PMax Insights (Campaigns > Insights and reports > select your PMax campaign), which groups matched queries into broader categories with associated conversion data. Review this monthly, and if a search category is clearly off-target — irrelevant to your catalog or converting at a fraction of your target ROAS — that's your signal to either tighten search themes toward more specific phrasing or escalate a negative keyword request if it's a brand-safety issue.
Building a negative keyword list from customer service patterns
Beyond Search terms reports, your own customer service inbox and product return reasons are an underused source of negative keywords. If customers frequently ask about compatibility issues, sizing problems, or confuse your product with a cheaper alternative, those confusion points often trace back to ambiguous search terms bringing in the wrong buyer. Add the specific confusing terms (a competitor's near-identical product name, or a generic category term your product doesn't actually fit) as negatives to reduce mismatched clicks before they become mismatched purchases and returns.
Shared negative keyword lists across campaigns
Rather than rebuilding a negative keyword list in every Search campaign, use Shared library > Negative keyword lists (Tools and Settings > Shared library) to build a master list applied across all Search and Shopping campaigns in the account. This keeps hygiene consistent as you launch new campaigns, and makes it far easier to add a newly discovered irrelevant term once and have it apply everywhere, rather than remembering to update five separate campaign-level lists individually.
The seasonal negative keyword trap
Negative keywords added for one purpose can inadvertently block valid traffic when circumstances change. A store that added 'free' as a negative keyword to block bargain-hunters may unintentionally block a legitimate seasonal promotion phrase like 'free shipping' if that ends up in a customer's search query and matches broadly. Audit negative keyword lists at the same cadence you audit keyword research — quarterly at minimum — and check the 'why this ad didn't show' diagnostic tool under Keywords for any keyword you suspect may be over-blocking during a promotional period.
Search themes and new product launches
When you add a new product to a PMax asset group, don't rely solely on the product feed data to carry search intent — proactively add 2-4 search themes specific to the new product's likely search phrasing, especially if the product name itself doesn't include the descriptive words a customer would search for (a proprietary product name like 'AeroFlex 200' won't surface for someone searching 'insulated water bottle' unless a search theme or feed attribute bridges that gap).
Negative keywords for brand terms you don't want conflated
If your store sells products under a house brand alongside other manufacturers' branded products, it's worth adding other manufacturers' brand names as negative keywords on campaigns specifically promoting your house brand, so those campaigns aren't credited with (and don't spend on) traffic actually searching for a competitor or supplier brand you happen to also carry. Keep separate campaigns or asset groups for third-party branded product lines so their search theme and keyword strategy can be tuned to that brand's actual search demand instead.
Reviewing match type creep over time
Because Google's exact and phrase match definitions have broadened to include close variants and related searches over the years, a negative keyword list built two or three years ago may now be blocking a wider (or narrower) set of queries than originally intended. Periodically re-verify that your negative keyword match types — negative exact, negative phrase, negative broad — still align with intent by spot-checking the Search terms report for near-misses that got through or over-blocked variants that should have been allowed.
Practical monthly checklist
A sustainable routine: review the PMax search category report and Search terms report for irrelevant traffic (15 minutes), add confirmed negatives to your shared negative keyword list (10 minutes), review any new products launched that month and add corresponding search themes to their asset group (15 minutes), and check account-level negative keyword requests if a genuine brand-safety issue has appeared. This keeps both sides of the equation — what PMax is invited to match, and what Search/Shopping explicitly blocks — current without turning into a full day of account maintenance.
Where this fits with automated tools
Adsify's optimizer runs every six hours across live campaigns, adjusting based on profit and POAS signals, but negative keyword hygiene for supplementary Search campaigns and search theme updates for new product launches are still worth reviewing manually on the cadence above, since they depend on judgment calls about brand safety and product-specific phrasing that go beyond what an automated bidding optimizer is evaluating on its cycle.