Negative keywords: the most underestimated factor in Google Ads

Imagine your Google Ads campaign is running, your budget is being spent and traffic is flowing to your website. Yet conversions remain disappointing. The cause is often surprisingly simple: a significant portion of your advertising budget is being consumed by search queries that will never lead to a purchase or lead. This is where negative keywords come in. They are the most underestimated factor in Google Ads and at the same time one of the most powerful levers for campaign efficiency. In 2026, using a well-thought-out negative keyword strategy is no longer a luxury but an absolute baseline requirement for any serious advertiser.

What are negative keywords and why do they matter so much?

Impact of negative keywords on campaign performance

ROAS improvement

+34%

Less irrelevant traffic

-58%

CTR increase

+45%

Conversion rate uplift

+72%

Budget efficiency

+85%

A negative keyword is a search term for which you explicitly instruct Google not to show your ad. While regular keywords determine which searches trigger your ads, negative keywords ensure your budget does not leak toward irrelevant or low-value queries. They act as a filter that guards the quality of incoming traffic.

The importance of this cannot be overstated. Google Ads works on broad interpretations of search intent. Especially with broad match and even phrase match, ads can appear for queries that are fundamentally distant from your offering. Someone searching for "free online Dutch course" has a completely different intent from someone searching for "online Dutch course for businesses". If you offer a paid corporate training, you absolutely do not want to pay for that first query. The word "free" should therefore be set as a negative keyword.

In 2026, advertisers who work systematically with negative keyword lists achieve on average 34% higher ROAS compared to advertisers who neglect this aspect. That figure alone makes it clear that this topic deserves the full attention of everyone working seriously with Google Ads.

The three types of negative keywords and when to use each

Just like regular keywords, negative keywords have three match types, each with its own function and application area. Understanding this difference is essential for an effective strategy.

• Broad match negative: Blocks queries containing all words of your negative keyword in any order. Use this for broad themes completely outside your offering, such as "free" or "job vacancy".
• Phrase match negative: Blocks queries containing the exact word order of your negative keyword. This is useful when you want to exclude specific word combinations without blocking too broadly.
• Exact match negative: Blocks only queries that exactly match the specified keyword. Use this when you want to block a specific term but allow variations.

Smartly combining these three match types is an art in itself. Most advertisers start with broad match negatives for clear exclusions (such as competitor brands or irrelevant sectors) and then refine with phrase match and exact match negatives for more granular control.

Common mistakes with negative keywords

Practice shows that even experienced advertisers regularly make the same mistakes with their negative keyword strategy. Awareness of these is the first step toward improvement.

• Setting too few negative keywords: Many advertisers launch a campaign with virtually no negatives. The search terms report is never consulted and budget evaporates on irrelevant clicks.
• Setting negatives at campaign level when ad group level is more appropriate: This can lead to blocking valuable queries for other ad groups that would actually benefit from them.
• Not using shared negative lists: Those managing multiple campaigns save enormous time by creating shared negative keyword lists that apply across all relevant campaigns.
• Forgetting to update the list periodically: Search behavior evolves. New irrelevant queries emerge. Those who do not regularly update their negative keyword list miss opportunities for further optimization.
• Being too aggressive in blocking: The reverse problem also exists. Over-blocking can cause valuable audiences to be missed. A negative keyword should never be added without analyzing search volume and intent first.

ToetsJeKennis.nl: negative keywords in practice

A concrete example makes the theory tangible. ToetsJeKennis.nl is an online platform offering knowledge quizzes and practice material for students and professionals. Their Google Ads campaigns target people actively looking for practice tests and knowledge assessments for specific subject areas.

At the start of the collaboration, it turned out that a significant portion of their advertising budget was being spent on queries like "take test for free", "test answers", "cheating exam" and "raise test scores". These searchers had a completely different intent from the target audience of ToetsJeKennis.nl. By building an extensive negative keyword list with terms like "free", "answers", "cheat", "solutions" and variations thereof, the share of irrelevant traffic dropped by more than half.

The result was impressive. The ROAS of the campaigns rose significantly, click costs decreased as quality scores improved, and the conversion rate increased because virtually all incoming traffic now consisted of people with genuine purchase intent. Moreover, with the same budget it was now possible to invest more in queries that actually mattered.

Negative keywords and Smart Bidding: a powerful combination

A misconception that we still frequently encounter in 2026 is that automated bidding makes negative keywords redundant. The opposite is true. Smart Bidding and negative keywords are complementary and reinforce each other. Smart Bidding optimizes bids based on signals about the probability of conversion. But if you feed the algorithm with irrelevant traffic, it learns from the wrong data.

Imagine using a target CPA strategy. Every time an irrelevant searcher clicks your ad but does not convert, it sends a negative signal to the algorithm. The result is that the algorithm bids less aggressively on terms that actually do matter. A clean negative keyword list ensures that the Smart Bidding algorithm learns exclusively from valuable interactions, which further increases bidding efficiency.

Comparison: campaigns with and without a negative keyword strategy

Feature	Without negative keywords	With negative keywords
Quality of incoming traffic	Mixed, many irrelevant visitors	High, intent-driven traffic
Cost per click (CPC)	Higher due to lower quality score	Lower due to higher quality score
Conversion rate	Low (1-2% average)	High (3-6% average)
ROAS	Suboptimal	34% higher on average
Smart Bidding efficiency	Limited by polluted data	Optimal with clean signals
Budget waste	Up to 40% of budget	Minimal, targeted spend

Advanced tactics for negative keywords in 2026

Once the basics are in place, you can move on to more advanced techniques. One of the most valuable is using campaign-specific negative keyword lists combined with a shared account list. This allows you to differentiate at campaign level (a brand campaign needs different negatives than a generic search campaign) while broader exclusions always apply to the entire account.

Another advanced application is setting up campaign exclusions based on audience signals. If audience analysis shows certain demographic groups consistently do not convert, you can consider adding specific search terms frequently used by these groups as negative keywords, or work with bid adjustments in combination with negative keywords for maximum control.

In 2026, it is also increasingly relevant to look at seasonal negative keywords. Think about temporarily adding keywords like "christmas gift" to your list if you sell a B2B product that is clearly not a gift item. These kinds of temporary, contextual adjustments can temporarily and significantly improve relevance scores.

Our approach at AdBrains combines AI-powered analysis with human expertise to continuously optimize negative keyword lists. Our AI methodology ensures that irrelevant search terms are proactively identified before they can cause significant budget damage, keeping campaigns performing at their peak at all times.

The investment in professional campaign management pays for itself because every euro of advertising budget works harder. A clean account with well-maintained negative keyword lists delivers structurally better results than an account running on autopilot without regular review of the search terms report. For more answers to common questions, visit our FAQ page.

Frequently asked questions about negative keywords

How many negative keywords should an average Google Ads account have?

There is no universal answer, but a healthy account typically has dozens to hundreds of negative keywords depending on the scale and diversity of its campaigns. A beginner can start perfectly well with 20 to 50 carefully chosen negatives and gradually expand based on the search terms report. Large e-commerce accounts with broad keyword coverage can easily reach several hundred negatives spread across shared lists and campaign-specific lists. The quality of negatives is always more important than the quantity.

Can Smart Bidding automatically manage negative keywords?

No, Smart Bidding does not manage negative keywords. Smart Bidding adjusts bids based on conversion signals, but blocking irrelevant queries via negative keywords must always be done manually or through AI-assisted tools. This is precisely why the two strategies are so complementary. A strong negative keyword strategy delivers better training data for the Smart Bidding algorithm, which raises bidding efficiency. See also our article on automated bidding for deeper insight into when Smart Bidding works best.

What is the difference between campaign-level and ad group-level negative keywords?

Campaign-level negative keywords apply to all ad groups within that campaign. This is useful for exclusions relevant to the entire campaign theme. Ad group-level negative keywords apply exclusively to that specific ad group. This is more useful when you want to prevent ad groups with overlapping keywords from cannibalizing each other's traffic. In practice, ideally you work with a combination of both levels, supplemented by shared account lists for universal exclusions that apply to all campaigns.

How quickly will I notice a difference after adding negative keywords?

The impact of negative keywords is almost immediately visible in the search terms report: the relevant queries will no longer appear. The broader campaign impact on metrics such as CTR, conversion rate and return on ad spend is typically visible within one to two weeks after implementation, depending on search volume. For smaller accounts with low volume, it may take four to six weeks before statistics are stable enough to draw reliable conclusions. Patience and consistent monitoring are key throughout this process.