You added a few negative keywords to stop paying for irrelevant searches. Now impressions are down, and you're wondering whether the cleanup went too far.
It's tempting to remove everything you just added and see whether traffic comes back. But that could reopen the searches you meant to exclude. And if something else changed that day, you could undo a useful exclusion without fixing the actual problem.
I'd start with a smaller question. Can you identify a search you want that one of those new negatives would block?
Fewer impressions leave part of the story missing
An exclusion is supposed to reduce your reach. If the impressions you lose came from people looking for something you don't sell, the lower count may be consistent with the change you intended.
The concern is losing opportunities to reach suitable customers. Total impressions alone won't tell you which happened, so give the review a business definition. A company that cleans office carpets wants enquiries from office managers. It doesn't want people shopping for secondhand desks, even though both searches might mention an office.
You can check that distinction before deciding whether to reverse the change. Here's how I'd work through it for a standard Search campaign.
Review the change before reversing it
1. Find out exactly what changed
Start with the date the decline began and the campaign or ad groups affected. Compare equivalent reporting periods, including the same weekdays, rather than a full week against a few unfinished days.
Open Change history from the Campaigns menu and inspect the changes around that date. Google lets you filter by campaign and review individual entries. Its Change history guide explains the available filters.
Look beyond the negative keywords. If someone also reduced the budget or changed a bid target, keep those changes in the investigation. A note saying that negatives were added on Tuesday doesn't isolate them as the cause of Wednesday's decline.
Save the recent exclusions and their match types in your existing account notes. You'll need the actual entries to check what they could remove.
2. Try the exclusions against searches you want
Choose some relevant queries from your earlier search terms report. Include searches associated with worthwhile enquiries when you have that information. You can also write realistic customer searches as checks, provided you label them as examples rather than observed traffic.
For each recent negative, ask whether its wording would exclude one of those wanted searches.
Consider an illustrative office-cleaning business. It sees the unwanted query used office desks and adds "office" as a negative phrase. That also blocks office carpet cleaning, a search the business wants. The shared word is enough to create a conflict.
A negative exact entry such as [used office desks] would exclude that complete query while leaving additional-word versions outside that entry's coverage. It also leaves other furniture searches to review. That's a tradeoff you can assess, rather than a reason to exclude every search containing office.
Google's Search rules distinguish negative broad, phrase and exact matching. Broad requires all the excluded terms in any order; phrase requires their sequence; exact covers the complete query without extra words. Synonyms and singular/plural alternatives need separate consideration, while casing and misspellings are handled automatically. Check the current negative-keyword rules here.
The examples above explain a possible conflict. They aren't a list to paste into your account, and they don't establish how much traffic your own exclusions removed.
3. Check where the negative applies
An exclusion can make sense for one service and interfere with another. If your business sells both cleaning services and equipment, an equipment exclusion intended for the cleaning campaign needs careful placement.
Inspect the affected ad group's negatives, campaign exclusions and any attached shared lists. Include account-level exclusions in the review. If you change a shared list, check its other campaign attachments before saving. Google documents exclusion levels and list attachments here.
Finding the same word in several places doesn't automatically mean the setup is wrong. What matters is whether an applicable exclusion conflicts with a search that belongs in that campaign. Removing one entry may leave another exclusion affecting the same query.
4. Follow other explanations when the exclusions don't account for the drop
If you can't find a plausible conflict, keep investigating. Don't widen eligibility simply because the timing looked suspicious.
Check whether the ads and keywords are eligible to serve, then follow the other changes you found in the account history. A new bidding target deserves attention if it coincided with the decline. When settings appear unchanged, consider auction conditions and changes in demand. Google's Search fluctuation guide covers these possibilities.
You don't need to change all of those things. Choose the next check that could support or weaken an explanation for the affected campaign.
5. Correct a specific problem and review the result
If you find a wanted-query conflict, correct the relevant wording or application level. Keep a copy of the previous entry and record why you changed it. Avoid combining that correction with unrelated bidding or landing-page changes if you want a clearer comparison afterward.
Then review both the unwanted traffic and the customer activity you meant to protect. More impressions after removing a negative show a change in delivery; they don't establish that the added traffic brought useful enquiries. Likewise, removing a conflict restores eligibility under that rule, without guaranteeing that an ad will appear.
Set the next review around your spending pace and the time enquiries take to develop. Record what you can verify, including anything that still leaves the cause uncertain.
If you want more practice deciding what to exclude, my free course Before You Add Another Negative works through those decisions with examples and a review card. Bring one recurring search pattern and check what your proposed exclusion would do to the customers you want to reach.