Tools in Microsoft Advertising for creating, editing, and optimizing ad campaigns
Good Morning,
Thank you for your question. the number of keyword recommended per adgroup depends on many factors, your bid to budget ratio, yoru goals for that adgroup. One thing that I see happen frequently is that the total bids on keywords can be close to or higher than the budget and this will cause the system to slow down or even stop serving to avoid going over you budget.
Strictly from a technical perspective the limit is 20,000 keywords per adgroup and 20,000 negative keywords per adgroup.
Some best practices for building your keyword list can be found here at Some hints for building a keyword list.
Consider your ad when choosing the keywords for you ad group. Are the words included in the ad? Or are similar word in the ad? If you have a long string of keywords, would it be best to use Broad Match Modifier to avoid mismatches when using the broad match type. See Using Broad Match and Broad Match Modifier.
Please do not hesitate to reach out to our customer support team for a more in depth review of your account.