Addy 
Addly 
Goalify 
Monet 
Reviso 
Key takeaways
- Add-ons are optional extras attached to a product the shopper already wants. Bundles are a new product made of several SKUs.
- Use add-ons when the extra is small, optional and would look silly as its own PDP (gift wrap, a spare cable, extended warranty).
- Use bundles when the combination is the point — a routine, a kit, a "complete the look" that you would be happy to stock as its own SKU.
- Do not run both on the same product page. Two offer types compete for the same increment and both convert worse.
A bundle says "this is the product". An add-on says "this product, plus a small yes". Mixing them on one page asks the shopper to solve two different problems at once. Most of them solve neither.
The test
Would you be willing to give the combination its own URL, its own photos and its own inventory? If yes, it is a bundle. If no — if the extra only makes sense attached to something else — it is an add-on.
Gift wrap is an add-on. A skincare routine of cleanser, serum and moisturiser is a bundle. A spare charging cable next to a lamp is an add-on. A "desk kit" of lamp, cable and bulb sold as one price is a bundle.
Why add-ons convert on the product page
The shopper has already chosen the parent. The remaining question is small. A checkbox is the right UI: low commitment, high clarity, no new product to evaluate.
That is also why add-ons fail when they look like products. A second product card with a price, a review stars row and a "learn more" link is a detour. Detours get skipped.
Why bundles belong in the catalogue
A bundle has a job the add-on does not: it can be found. It can rank. It can be advertised. It can have a margin structure you planned, rather than a last-second checkbox.
If 40% of buyers of A also take B, stop hiding B as an add-on and make A+B a product. You will sell it to people who never visited A's page.
Do not stack
The product page can carry one incremental offer besides the buy box. If you already have a bundle selector, do not also drop three add-on checkboxes. If you already have add-ons, do not also run a "frequently bought together" strip that repeats the same SKUs.
Pick the structure that matches the SKU. Kill the other one. Average order value goes up when the page asks one extra question, not four.
Frequently asked questions
Is a frequently-bought-together widget a bundle or an add-on?
It behaves like an add-on — the shopper can take or leave the extra SKUs — even if you discount it like a bundle. Treat it as an add-on in the page layout: after the buy box, not instead of it.
Should add-ons be discounted?
Rarely. The shopper already wants the parent product. Discounting the extra trains them to wait for a deal on something they would have added at full price.
Can I turn a popular add-on into a bundle later?
Yes, and you should once a pair starts selling together more often than not. At that point the combination is the product, and a bundle price is honest.
Where do add-ons go on the page?
Directly under the add-to-cart button, as a checklist, not in a related-products carousel at the footer. Footer carousels are for browsing. Add-ons are for this purchase.
