Google Ads announced an upgrade to Similar Audience Segments on November 1, 2022. They have announced that Similar Segments will be removed in August, 2023 and they will no longer be created by May, 2023. If advertisers are using Similar Segments then their segments will be gone in current campaigns starting August of 2023.

Google Ads announced that starting May 2023, new similar audiences segments will stop being created, and your current similar audiences segments will no longer be allowed to be added to campaigns.

While Similar Segments are being removed, it seems like a privacy move. Google Ads says that "Optimized targeting can help you find new and relevant audiences that are likely to convert without relying on third-party cookies."

Display, Discovery, or Video Action campaigns:
- Use optimized targeting & smart bidding

Awareness and Reach or Consideration video:
- Use audience expansion

Search and/or Shopping campaigns:
- Use smart bidding