Most Google Ads beginners think campaign optimization means adding more keywords. It doesn't. Pull up your Search Terms Report and you'll find a chunk of your budget going to people who typed "free", "how to DIY", or a competitor's name. They clicked. You paid. None of them bought. Negative keywords are the filter that stops this.
What negative keywords actually do
A negative keyword tells Google: "If someone's query contains this word or phrase, don't show my ad."
Simple example: you're running a custom web design service priced at ฿30,000–80,000 per project. Your campaign targets "web design services". Without a negative, Google will match your ad to "free web design services" queries too. Every click from someone hunting a freebie costs you real money.
The three match types
Negative keywords use the same match-type logic as regular keywords — and the choice matters.
Negative Broad Match — blocks any query containing that word, in any order
- Add:
free - Blocks: "free web design", "web design for free", "free logo maker"
Negative Phrase Match — blocks queries where the phrase appears consecutively (recommended)
- Add:
"how to" - Blocks: "how to build a website", "how to make a logo for free"
- Doesn't block: "someone to help with my website"
Negative Exact Match — blocks only that exact query, nothing broader or narrower
- Add:
[free web design] - Blocks: only the exact query "free web design"
Start with Negative Phrase Match. It's broad enough to catch obvious variations but precise enough that you won't accidentally block good traffic.
Finding junk: the Search Terms Report
Before building your negative list, see what Google is actually matching you to. Don't guess.
Steps:
- Open Google Ads → Campaigns → select your campaign
- Go to Keywords → Search terms
- Set the date range: last 30 days
- Sort by Cost descending
- Flag every query where Cost is high and Conversions = 0
Add those as negatives. That's your first 30 minutes of cleanup done.
Common categories to block
Some terms you can add on day one without waiting for data:
"Free" / "free trial" / "no cost" — hunting for freebies, not paid services
"Review" / "comparison" / "vs" — researching, not ready to buy today
"How to" / "tutorial" / "DIY" / "course" — wants education, not a vendor
Job-related terms — "salary", "jobs", "hiring", "apply" — broad match keywords can pull in job seekers who aren't your customers
Competitor brand names — unless you're running a deliberate conquest campaign
Low-price qualifiers — "cheap", "budget", "under ฿1,000" — if your pricing doesn't match what they want
The trap nobody talks about
A negative keyword list isn't a set-and-forget task. Every two weeks, run through the Search Terms Report again.
Google's Broad Match and Phrase Match keep expanding their interpretation of relevant queries. A keyword you added months ago now matches searches it never used to. New junk terms keep appearing. Skip maintenance for two months and you'll find meaningful budget quietly drifting to non-converting traffic — and you won't notice until you audit.
Quick reference
| Goal | Use |
|---|---|
| Block every variation with that word | Negative Broad |
| Block a phrase in consecutive order | Negative Phrase (recommended) |
| Block that exact query only | Negative Exact |
| Block across entire campaign | Campaign-level negative |
| Block in specific ad groups only | Ad group-level negative |
| Reuse the same list across campaigns | Negative Keyword List |
What to do next
Open the Search Terms Report for your highest-spend campaign. Filter for the last 30 days, sort by Cost, and flag every query with 0 conversions. If there are more than three, you're paying for clicks that won't convert.
If you're using AdBlueprint, check the Keyword Strategy section in your Blueprint — it maps the intent category your campaign is targeting, so you know which negative keyword clusters to tackle first.