This article explains how to troubleshoot when negative keywords aren't working as expected.
Common issues and misconceptions with negative keywords
1. My ads are showing on searches that should be blocked by a negative keyword
Negative keywords don’t match to variants
Negative keywords work differently than their positive counterparts. Positive keywords can match to searches that are similar, but not identical to the targeted keyword, such as misspellings, reordered words or same meaning terms. Negative keywords don't match to these variants.
This means that if you want to prevent an ad from serving on an eligible search, you need to exclude the specific search terms exactly. For example, if you add the negative broad match keyword -house to your ad group, it will only prevent ads from serving on searches that contain the term ‘house’ exactly. This means that an ad wouldn’t be eligible to serve on ‘red house’ but it could serve on ‘blue houses’. Learn more About negative keywords.
Queries over 16 words long
Your ad might still show when someone searches for a phrase that's longer than 16 words, and your negative keyword follows that 16th word. Let's say that your negative keyword is "discount". Your ad can show when someone searches for "nice clean hotel rooms or bed and breakfast rentals in Bournemouth Dorset close to beach discount" because your negative keyword is the 17th word in the phrase. On the other hand, we won't show your ad when someone searches for "nice clean hotel rooms or bed and breakfast rentals in Bournemouth Dorset close to beach discount" because your negative keyword is the 16th word in the keyword.
Check the date range
If you identify a search in the search terms report that should have been excluded by a negative keyword, make sure that you are looking at the correct reporting date range. The Change history tool, accessible under 'Campaigns' in the Main menu, can be used to check the date when the negative keyword was applied to the ad group or campaign. For example, if you are looking at the search term report for the last three months, but the negative keyword was applied two weeks ago, it’s expected that you would find the negative term in your report.