Most of the time this comes down to one of four things: your keywords are set to broad match and Google is matching on “intent” rather than wording, your negative keywords don’t cover close variants or misspellings of the terms you’re trying to block, a negative keyword list exists but was never applied to the campaign that’s actually running, or the irrelevant traffic is coming from Performance Max, which pulls search terms from a different and less visible pool than standard Search campaigns. Fix the match type and negative keyword setup first, because that’s where almost all of this traffic originates.
If your keywords are on broad match (no quotes, no brackets), Google isn’t matching on your keyword’s wording at all. It’s using your keyword as a signal, combined with your landing page, ad copy, other keywords in the account, and the searcher’s history, to decide what queries are “related enough” to show your ad for. That’s intentional. Broad match is built to find volume beyond the literal keyword, and it will happily serve a search term that shares almost no words with what you typed if Google’s model thinks the intent is similar.
This is why a plumbing company bidding on “emergency plumber” can end up showing for “24 hour electrician” or “appliance repair near me.” None of those share a word with the keyword, but Google judged them close enough in intent. The fix isn’t to abandon broad match (it genuinely finds good traffic when it’s paired with strong Smart Bidding and enough conversion data), it’s to check the Search terms report weekly while a broad match campaign is new, and to be fast and aggressive about adding negatives for anything off-target before it burns meaningful spend.
This trips up a lot of people because it runs backwards from how positive match types work. A positive keyword on broad or phrase match will automatically pick up plurals, misspellings, and close variants of what you typed. A negative keyword does not get that same courtesy. If you add “free” as a negative, it will not automatically block “freee,” “frees,” or close misspellings. You have to add the actual variant as its own negative, or the search term will keep slipping through even though you were sure you’d already excluded it.
Google’s own documentation on this is blunt about it: negative keywords are evaluated against the literal query, not an expanded set of variants. So if you’re confident you blocked a term and it’s still showing up in your search terms report, check the exact spelling and word order of what’s actually being searched versus what you entered as a negative. A negative broad match on “house” blocks any query containing the word “house,” but it won’t block “houses” as a separate stemmed form unless Google’s literal matching happens to catch it, and it won’t catch an unrelated phrasing of the same idea.
Negative keyword lists live at the account level in Google Ads, which makes them easy to build once and reuse everywhere. The problem is that building the list doesn’t do anything on its own. A negative keyword list only affects a campaign once you’ve explicitly applied it to that campaign under its negative keywords settings. It’s extremely common for someone to build a solid shared negative list early on, apply it to their main campaigns, then launch a new campaign months later and forget to attach the list. The new campaign runs with zero negative keyword protection even though a perfectly good list is sitting right there in the account.
If irrelevant search terms are showing up on one specific campaign while your others look clean, this is the first thing to check: open that campaign’s negative keywords, and confirm the list you think is protecting it is actually linked there.
If the irrelevant traffic is coming through a Performance Max campaign, the rules change. For a long time PMax campaigns were capped at just 100 account-level negative keywords and didn’t support negative keyword lists at all, which made it genuinely hard to clean up bad traffic at any scale. Google raised that limit to 10,000 negative keywords per campaign in March 2025, which helps, but negative keyword lists still aren’t supported inside PMax itself. You add negatives directly to the PMax campaign (through a Google Ads rep request for campaign-level negatives, or via account-level negatives that apply automatically to the Search and Shopping inventory inside any PMax campaign).
PMax negative keywords only affect the Search and Shopping inventory inside that campaign. They do nothing to control which Display, YouTube, or Discovery placements it chooses, so a PMax campaign can still look “off” even after you’ve cleaned up its search terms.
To see what PMax is actually matching on, use the Insights tab inside the campaign, which shows a sample of search categories and terms. It’s not as complete as the Search terms report on a standard Search campaign, but it’s the closest visibility you’ll get, and it’s worth checking every week or two on any PMax campaign that’s spending real budget.
Negative keywords are only evaluated against the first 16 words of a search query. If someone types an unusually long search phrase and the term you’re trying to block falls after word 16, your negative won’t catch it. This is rare in practice since most real searches are short, but it occasionally explains why a negative you’re certain should be working isn’t.
Treat your search terms report as ongoing maintenance, not a one time setup task. Review it weekly for the first month of any new campaign and monthly after that. When you find an irrelevant term, add the exact phrase as a negative (not a shortened version of it), check whether it belongs on a shared list so future campaigns inherit the protection, and confirm that list is actually attached to every campaign you expect it to cover. If the noise is coming from Performance Max, lean on the Insights tab and account-level negatives since you won’t have a search terms report to rely on there. None of this is glamorous work, but it’s the difference between an account that slowly cleans itself up and one that keeps bleeding budget on the same irrelevant clicks month after month.
