Addy 
Addly 
Goalify 
Monet 
Reviso 
Key takeaways
- One overlay, one product, one action. A second product turns a decision into a catalogue.
- Pick the offer from what is already in the cart or on the page — not from a merchandiser's favourite SKU.
- The primary button is "Add". The secondary action is dismiss. A "See all" link is how people escape into browsing.
- If you cannot name why this SKU belongs with this cart in one sentence, it is not the offer.
A popup has a few seconds and one job. That job is not "present the catalogue". It is "do you want this, yes or no".
Two products in the overlay doubles the reading and halves the chance of a yes. Shoppers who would have added the first SKU start comparing. Comparison is browsing. Browsing is how overlays get closed.
One sentence of why
Before you ship an offer, write: "Because the cart contains X, we are offering Y." If X is empty (a generic sitewide popup), you do not have an upsell. You have an ad.
Because they added the mug, we are offering the 250g beans. Because they added the running shorts, we are offering the same-brand socks. Because they added a gift-boxed candle, we are offering wrap. Those sentences are offers. "Our bestsellers" is not.
The button
Primary: Add (and, if you must, the price). Secondary: close. No "continue shopping" that opens a collection. No "view product" that dumps them on a PDP and kills the cart they came from.
If they need to read a full product page to decide, the popup picked the wrong SKU. Pick a lower-consideration attachment.
Discount last
Try the pair at full price. If attach rate is real, keep it. If it is near zero, a small bundle-style discount can be the difference — but it should be the last lever, not the first, because popup discounts become expected.
Measure one number
Attach rate of this SKU from this trigger. Not popup CTR. Clicks that do not add are still a no, they just took longer.
Frequently asked questions
Can I show a bundle of two items in one popup?
Yes, if it is one offer — a set with one price and one add button. Two separate products with two add buttons is two offers.
What if I have several good attachments?
Rank them, show the winner, keep the rest for the cart or the product page. The popup is not your merchandising dump.
Should the popup include a discount?
Only if the pair does not attach at full price. Discounts in popups train people to wait for the overlay. Try without first.
Is a carousel of offers okay?
No. Carousels in popups are how take rate dies. If you need a carousel, the offer is not ready.
