Anonymisation means altering personal data so that it can no longer be linked to an identifiable person — either directly or indirectly. Once data has been fully anonymised, its processing is no longer subject to the GDPR.
In Web analytics anonymisation plays an important role—for example, by truncating IP addresses or removing identifying characteristics. Many tracking tools offer suitable features to support privacy-compliant analytics.
Important: Anonymisation should not be confused with pseudonymisation, where an indirect link to an individual remains possible.