Every price comparison on this site rests on one claim: that the product on one marketplace and the product on another are the same thing. That is a strong claim, so this page sets out exactly what we check, what each check can tell you, and — the part most comparison sites leave out — what we cannot establish at all.
The reasoning behind every match confidence figure on the site.
A guarantee. It is a statement of how much evidence sits behind a match.
A name and a photograph are the two easiest things for a merchant to change, so neither settles a match on its own. Each check below answers a different question, and each has a limit we are explicit about.
Every photograph of the product is compared against every photograph of every candidate, by two independent visual models. Products made from the same mould photograph alike in ways that survive different lighting, backgrounds and crops.
A measure of how closely two objects resemble each other, across every image either listing publishes.
That they are the same object. Merchants reuse manufacturer photography freely, so the same picture can sit above a different size, material or product entirely.
The candidate has to be the same kind of thing. This is the check that catches what image matching alone lets through — a storage bag photographed like a bath toy scoop, beads of one material listed under beads of another.
A hard stop. If the type does not match, there is no match, whatever the pictures look like.
That the quality is the same. Two items can be the same type and the same shape and still differ in what they are made of.
We look for every merchant carrying the unit rather than stopping at the first. A product listed by several independent merchants at similar prices is a different proposition from one listed once.
How many merchants carry it, how long each has been trading, and what buyers report about them.
How your particular parcel will arrive. A merchant's history describes the merchant, not your order.
A listing is not one price. It is a set of options — size, colour, count, bundle — each priced differently, and the figure you see first is usually the lowest-priced of them. We read the option matrix on both sides, pin the option that corresponds, and read how many units are actually in the box before any percentage is calculated. A six-pack against a single unit is not a saving.
A comparison between two specific options, on a stated basis — per item, or one unit against a whole pack — shown on every product.
What it costs to get it to you. We compare item prices; we do not calculate shipping, duties or taxes to your country.
The single number on a listing is the lowest-priced thing that listing sells. It is rarely the thing you came for.
A pack of ten and a single unit can sit on the same page under the same photograph, and the price shown in search results belongs to whichever costs least. The widest single listing we have measured runs 79× from its lowest-priced option to its highest. Comparing two listings by their headline figures therefore compares two objects that are not the same object, which is how a comparison can be arithmetically correct and still wrong.
So the option is pinned before anything is compared. We read what each side actually ships — how many, what size, what is included — and state the basis on every product: per item when both sides sell the same unit, or one unit against a whole pack when they do not. Where the contents cannot be read on both sides, no percentage is published at all.
This is the part that changes an answer. A pack of six watch bands at $8.49 works out at $1.42 each, which beats a $2.57 single elsewhere — so the mainstream listing wins, and we say so. Read on the sticker price alone, the same two listings look like a saving of more than two thirds in the other direction.
The four checks combine into a single number between 0 and 100. It describes how much the evidence agrees — not how much we would like it to. The median across everything we have matched so far is 79%.
Above a floor, a match is described one of two ways, and the difference matters more than the number does:
Same mould, same construction, usually the same manufacturer listing with a different logo on the box. This is the only case where we use the word identical, and the only case a saving figure is described as being for the same design.
It does the same job to the same specification, but it is not the same object. Worth buying, often worth much less money, and we label it separately so you are never told you are getting the same thing when you are not.
Same mould, same construction, usually the same manufacturer listing with a different logo on the box. This is the only case where we use the word identical, and the only case a saving figure is described as being for the same design.
It does the same job to the same specification, but it is not the same object. Worth buying, often worth much less money, and we label it separately so you are never told you are getting the same thing when you are not.
Roughly 47% of the matches we publish are Same design; the rest are Equivalents. Below the floor we publish nothing at all — an uncertain match is worse than no match, because it is the one that sends you to the wrong product.
We never hold the product. Everything on this site is drawn from listings, photographs and what buyers report, which leaves real gaps. These are the ones worth knowing about before you spend money.
A photograph shows shape and finish. It does not show what a plastic is, how thick a steel is, or how a fabric is woven. Two objects can match closely on every image and still differ in what they are made of.
We do not test anything, and we do not verify certification claims. In categories where testing and liability are a genuine cost — child safety, electrical, anything load-bearing — that is a large part of what a brand premium buys, and we say so rather than treating the objects as interchangeable.
A merchant who shipped well last year may not this year. Trading history and buyer reports describe a pattern, not your particular parcel.
Listings change under the same address — a merchant can swap the unit behind one. We re-check on a fixed cycle, but between checks a listing can become something else.
We read what reviews say rather than what they average, which helps. It does not let us certify that any individual review is real.
We compare the price of the item. Shipping, duties and local taxes are not calculated, so the figure you see is the price of the object and not the price of getting it to your door.
For a branded product we can tell you an identical-looking unit is listed elsewhere. We cannot tell you whether that particular merchant is authorised to sell it.
Prices move, stock runs out and merchants close. Every figure on this site carries the date it was checked, and that date is the whole of what we are claiming.
Uncertainty is common. What matters is what happens next, so these are fixed rules rather than judgement calls.
The fourth rule is not a formality. On the categories we have worked through so far, close to half of everything we check ends with us telling you to stay where you are. A comparison that can only ever reach one conclusion is not a comparison.
The catalogue is re-checked completely every 14 days. One fourteenth of it is checked each day, so something is always being verified and nothing waits longer than one cycle.
Each block is one day of the cycle. Today's slice is highlighted.
Every listing shows its own date. We would rather tell you a price was checked six days ago than imply it is live. Prices move, and a comparison you cannot date is a comparison you cannot check.
Everything above, applied to a product you can open and check for yourself.
TOHIBEE swimming turtle bath toys, 3 pack — Amazon lists a pack of 3 at $9.99, which is $3.33 each. We found the same design at $2.09 each, carried by 8 merchants.
Combined confidence 90%. The saving is stated per item, because Amazon sells this one in a pack and the alternative does not — comparing the sticker prices would have produced a much larger number and a much less useful one. See the full comparison →
On a product page, a cluster page or the home page, the match confidence figure is a link back to this page. If a number is being shown to you, the reasoning behind it is one click away.
Questions this page does not answer are covered in the common questions on the home page, or you can write to us.