Salesforce Duplicate Rules
What Is Duplicate Rules?
Duplicate rules detect when a user is about to create or edit a record that closely matches an existing one, based on matching rules you define, and can either block the save, warn the user, or simply log it.
Why It Matters
Duplicate records are one of the most common data quality problems in any CRM -- two reps creating the same lead independently, or a contact re-entered with a slightly different email format. Left unchecked, duplicates fragment activity history and skew reporting.
How to Set It Up
First create a matching rule (Setup -> Duplicate Rules -> Matching Rules) that defines what counts as a likely duplicate -- exact match on email, fuzzy match on name, etc.
Activate the matching rule once it's configured and tested.
Create the duplicate rule itself, selecting the matching rule to use and the object it applies to.
Choose the action: Block prevents the save entirely, Allow with alert lets the user proceed but warns them, and you can scope this differently for different user profiles.
Activate the duplicate rule and test by attempting to create an intentional near-duplicate record.
Common Mistakes to Avoid
Setting every duplicate rule to Block without an override path frustrates users in genuinely valid edge cases (two different people who happen to share a name and company). Most mature implementations use Allow with alert for borderline matches and reserve Block only for exact-match scenarios like duplicate email addresses.