Koi is a free Chrome extension designed to enhance your online shopping experience by maximizing credit card rewards. Users can easily select their credit cards through the Koi extension home page, allowing the tool to identify the card that offers the highest cash back during the checkout process. This feature ensures that users make the most out of their credit card rewards.

The extension works by analyzing the merchant category of each website visited and cross-referencing it with the rewards programs linked to the user’s credit cards. By doing so, Koi helps users earn the maximum cash back and rewards available for their purchases, streamlining the payment process and enhancing overall savings.