Adding under-performing keywords as negatives to Amazon Ads campaigns is essential to optimizing campaigns (see Amazon Advertising FAQs for a quick primer on how keywords work).
Add the right keywords, and you can cut out a lot of wasted spend. Search terms that produce no revenue and take up sizable spend are ideal candidates. Supported match types for negative keywords are described below.
Add the wrong keywords, and you could be cutting out a lot of relevant searches and hurt performance. For instance, let us assume you were selling cordless phones. Adding “cord” as a negative phrase keyword would block all keywords that have “cord” in them (example: cordless phone, phones without cord). This is also called keyword conflict. Amid the sheer volume of things you are doing to optimize campaigns, keyword conflicts can creep in occasionally.
Review your negative keywords list periodically and eliminate keyword conflicts. Pay special attention to Negative Phrase keywords.
Related Article: Don’t Mix Brand and Non-Brand Keywords in the Same Campaigns