I would like to use an external id which I've also marked as unique to prevent importing duplicate leads.

Does the Import Wizard respect the uniqueness constraint on custom fields? And will the import only skip duplicate records, or will it fail the entire import?

1 Answer 1


Per this documentation, it will respect the uniqueness of the external ID. https://na14.salesforce.com/help/doc/en/faq_import_general_what_is_an_external.htm

To my knowledge, only the duplicate records will be skipped.

  • 1
    If the field is set as Unique, then the rows that would violate the constraint are errored out. This won't prevent the remaining leads from saving, assuming there are no other errors; poorly written triggers can block up to 200 records on the import wizard if there is a fatal uncaught exception. This is implemented as a database-level index, so the wizard will honor the unique constraint.
    – sfdcfox
    Aug 15, 2013 at 18:12

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