Cheapest-item-free is the quantity offer with the most predictable cost. The shopper picks any three qualifying products and the cart discounts the lowest-priced of them to $0. Because the discount always lands on the cheapest line, your worst case is capped — unlike a flat percentage, which costs you most on your most expensive carts.
Define the qualifying set. A collection, a tag, or specific products. Only items inside the set count toward the quantity and only they can be the free one.
Set the quantity. Buy 2, 3, or 4. Three is the common choice because it reads as generous without discounting half the cart.
The cart resolves the cheapest line. When the quantity is met, the lowest-priced qualifying item is discounted to $0 — recalculated live as the shopper changes the cart.
Repeat or cap. Decide whether a cart of six gets two free items or just one. Both are valid; only one matches your margin.
Compare two offers on a cart of three items at $20, $30, and $90. "Cheapest free" costs you $20 — 14% of the cart. "20% off three or more" costs you $28, and the more expensive the cart, the wider that gap grows. The percentage discount is cheapest where you least need help and most expensive where your margin was already healthiest in absolute terms.
Cheapest-free also reads better. "Free" is a categorically different word from "20% off" — it removes the mental arithmetic and it makes the third item feel like a decision about whether to accept a gift rather than a decision about price. That framing is why the mechanic survives in retail decade after decade.
The trade-off is self-selection. Shoppers quickly learn to add a cheap item to collect the discount, which is why the qualifying set matters more here than in any other offer type.
The qualifying set is your cost control. A set with a wide price spread invites gaming: if a $4 keychain qualifies alongside $90 jackets, every three-jacket cart will acquire a keychain and nothing will be free that you minded giving.
The question every merchant hits in week one: a shopper adds six qualifying items — do they get one free or two? If the offer repeats, your cost scales linearly with cart size and large carts become your least profitable orders. If it does not repeat, your most enthusiastic shoppers feel short-changed at exactly the moment they were buying the most.
The usual resolution is to let it repeat but cap it — two applications per order, say — which keeps the large cart feeling rewarded without an open-ended liability. Whichever you choose, state it in the cart copy. "Cheapest of every 3 free" and "cheapest of your first 3 free" are both honest; only one matches your rule.
Cheapest-free, BOGO, and volume discounts all reward quantity, and they compete for the same slot in the shopper's attention. A rough guide: use BOGO when you want a specific second product moved, cheapest-free when you want quantity without dictating which products, and volume discounts when the same SKU is bought in multiples.
Running two of them at once on overlapping collections produces carts where the rules disagree. Offer priority rules settle which fires, and you should set them before launch rather than after the first confused support email.
Shopify's Buy X Get Y automatic discount can discount a specified Y product, but it does not resolve "whichever item in the cart is cheapest" across a qualifying set, and it will not recalculate as the shopper edits the cart. That dynamic resolution is what an app adds.
The qualifying set. Keep the price spread inside it narrow and exclude low-priced or already-discounted products, and the cheapest qualifying line stays close to the rest of the cart in value.
That is configurable. Repeating scales your cost with cart size; not repeating can feel stingy on large carts. Capping repeats at two per order is a common middle path. Whatever you choose, say it in the cart copy.
By the line price of qualifying items at the moment the cart is evaluated, recalculated whenever the cart changes. If a product's variants differ in price, qualify at the variant level.
Yes — and you usually should. A collection-scoped offer turns the mechanic into targeted inventory movement with a predictable cost per unit.
It depends on what else is running and on Shopify's combination rules for the discount types involved. See discount stacking for which combinations Shopify permits, and set an explicit offer priority so only one quantity offer fires per cart.
Yes. Every NUO AI feature is included at $0 — no paid tier, no order cap, no revenue share.
