Where can I view promotion code usage for a campaign?

Merchants can view promotion code usage for a specific campaign by downloading the order report:

To view the promotion code usage for a campaign:

1. In the left sidebar, click Orders.
2. Select the relevant Campaign ID.
3. Click Download in the top-right corner.
4. Select Orders with Custom Fields.
   

Open the export and check the Applied Discount Code column to see all discount codes used.