If you have a Pro Plus or Premium license, the same key can be used across multiple PCs, Macs, and Android devices [5.18, 5.21].
If you bought a physical copy, the key is usually on a card or sticker inside the box [11]. Activation Steps for PC and Mac Ccleaner pro license key
How to Enable CCleaner License After Purchase ... - LeetCode If you have a Pro Plus or Premium
If you've lost your email, you can use the official CCleaner License Lookup to retrieve it using your registered email address [5.3, 5.6]. and Android devices [5.18