Some of my contacts are displayed twice in my address book — what can I do?

You can get rid of duplicate contacts by deactivating the setting “Show inactive IDs” (Android) or by activating the setting Hide Stale Contacts (iOS) in Settings > Appearance. Stale contacts are IDs that haven't been used for more than three months. Therefore, it might take a while for contacts to be marked as inactive.

Alternatively, you can navigate to a contact’s detail view, activate “Exclude from auto sync,” delete the contact, and it won’t show up again when performing contact synchronizations.