The CSV user importer matches existing users only by primary email address. Include each user's existing primary email to avoid duplicates. You can merge duplicates you already have from the user's profile.
How the importer matches users
If the primary email matches an existing user, that user is updated.
If the email is missing or different, a new user is created, even when the name and other details are identical.
Import users without creating duplicates
Always include each user's existing primary email.
Don't import users without an email.
The importer can't change a primary email, because it's the match key.
The update mode that updates missing values only fills empty fields.
To keep fields current, such as a department or area, use an update mode that overwrites the values with the CSV.
Merge duplicate users
Open the user's profile.
Click the three dots, then Merge.
Find the other user by ID.
When you merge:
The record you keep retains its primary email. The other addresses become secondary emails.
All tickets raised by the other record move to the kept record, with their messages and attachments.
Tickets where the other record was CC'd also move across.
Organization and custom fields stay as they are on the kept record. They're only copied from the other record where the kept record has no value.
Labels, notes, and usergroups are combined.
If you want the other record's email as primary, keep that record instead. Or change the primary email after merging.
💡 Note: Only merge when you're sure it's the same person. Merged users get access to each other's tickets.