Both Fathom [1] and Plausible [2] claim to be GDPR compliant, but they are not.

They use a technique called "device fingerprinting" by collecting online identifiers, such as IP addresses, and browser characteristics for identification. Thus user consent is needed.

1: https://usefathom.com/gdpr-ccpa-pecr-compliant 2: https://plausible.io/data-policy