Discount codes
Set the amount, cap the uses, give it an end date — and see how many were redeemed instead of wondering whether anyone used it.
Whichever suits the product; you set the number.
Cap the uses and the date so a code can't outlive the campaign.
See how many were redeemed and what they were worth.
On physical orders the postage survives the discount, because the courier still charges you.

0%
platform fee on any plan
~1 min
to claim a link and publish
10
product types on one page