The idea in one sentence
Negative keywords are terms you tell the platform not to show your ads for. If a search contains one of them, in the way the match type allows, your ad is not eligible for that search.
That sounds like a small setting, but it protects the budget from a steady leak. Every irrelevant click costs the same as a relevant one.
Why irrelevant searches slip in
When you bid on a keyword, the platform may show your ad on searches that are related but not what you meant, especially with looser match types. The same words can mean quite different things.
Some made-up examples for a business that sells paid accounting software to small firms:
- “free accounting software”: the searcher wants something at no cost.
- “accounting jobs”: the searcher wants employment, not software.
- “accounting software tutorial pdf”: the searcher wants a learning resource.
- “accounting software for hospitals”: the searcher is outside your market.
Each of those searches might be triggered by a broad keyword such as “accounting software”. If your clicks cost 2 each, 50 such clicks cost 100, with essentially no chance of a sale. That is the kind of waste negative keywords are meant to prevent. The numbers are illustrative.
Where to find candidates
The search terms report
Platforms generally provide a report listing the actual queries that triggered your ads and what they cost. This is the most direct evidence. Review it regularly, particularly in the first weeks when settings are new. Look for queries that:
- show intent you do not serve (jobs, free, DIY, second-hand, reviews of a competitor, if irrelevant to you);
- refer to a product, location or category you do not offer;
- have spent money with no conversions and little reason to expect any.
Be careful not to exclude a term based on one or two clicks. A search that looks odd may still convert, and a single result is weak evidence.
Brainstorming in advance
Before launch, list words that suggest the wrong audience for your offer. Typical groups include free, cheap (if you are premium), jobs, training, salary, definition, template, and any specific places or product types you do not cover. Adding these early prevents some of the waste.
Competitor and brand names
Decide deliberately whether you want your ads to appear for other companies’ names. Using competitor names in ad text can raise policy and legal issues, and results are often poor. Check the platform’s rules and the rules that apply to you; this is not legal advice.
Match types for negatives
Negative keywords have their own match types, and the behavior can differ from the rules for ordinary keywords. A negative keyword set to a loose style may block only searches that include all of its words, in any order, while exact style blocks only that precise query. Close variants, such as plurals, may or may not be covered automatically. Details vary by platform and change over time, so read the current help pages and test with the search terms report.
A useful habit: start with narrower negatives, because an over-broad one can block searches you actually want. For example, excluding “jobs” is probably safe for a software company, but excluding “software” would block everything.
Organize them
- Campaign or ad group level: use these when a term is only irrelevant in one part of your account. A word like “repair” may be unwanted in a sales campaign but wanted in a service one.
- Shared lists: many platforms let you build a list once and apply it to several campaigns. This suits universal exclusions such as jobs, free and unrelated categories.
- Overlap between ad groups: if two ad groups could trigger on the same search, a negative can steer the search to the better-fitting one. Do this carefully, because mistakes can leave a valuable search without any ad.
Keep a record of what you added and why, so that later you can understand the choices and undo them if the business changes. A simple testing log approach works well.
The risks of overdoing it
Negative keywords are powerful because they remove traffic. Too many, or too broad, and you can shrink your reach and starve a campaign. Signs of over-exclusion include a sudden fall in impressions after list changes, and conversions that disappear alongside the irrelevant clicks. When in doubt, remove the doubtful term and see what happens.
Remember also that language shifts. A word that was irrelevant last year may describe a product you now sell.
A simple routine
- Add a starter list of obvious exclusions before launch.
- Check the search terms report a few times in the first two weeks, then weekly or fortnightly.
- Add clearly irrelevant queries as negatives, at the right level and match type.
- Note any queries that surprise you in a positive way; they may deserve their own keywords and ads.
- Review the lists every few months for terms that are no longer right.
Negative keywords reduce waste but do not guarantee a profitable campaign. That still depends on your offer, the landing page, the price you pay for clicks and the cost per acquisition you can afford. Results vary by business and market.