Merging duplicate accounts, contacts, and leads
Key Takeaway
In a merge, data in hidden or read-only fields comes from the principal record. The merged record still keeps the Created By user and Created Date of the oldest record in the merge, no matter which record is the principal.
Merging combines duplicate account, contact, or lead records into one record. You choose which record to keep. Salesforce moves related items onto it and sends the other records to the Recycle Bin. What survives the merge differs by object, and sometimes by interface (Lightning Experience or Salesforce Classic), so the record you choose to keep matters.
Handling duplicates one at a time or across the org
You can handle duplicates one at a time or across the whole org. Each approach needs different setup.
If you want to handle duplicates one at a time...
Activate duplicate rules and the Potential Duplicates component, which control whether and when reps can create duplicate accounts, contacts, and leads. Give reps permission to merge duplicate leads, business and person accounts, and contacts.
If you want to handle duplicates across the whole org...
Run duplicate jobs. Share the results with reports. Merge the duplicates through duplicate record sets.