A discount badge on 11 November compares the sale price with a crossed-out price the seller chose. This page compares it with something the seller did not choose: the price we recorded for the same listing in the two weeks before the sale.
That is the morning after the first full sale day, and the figures are updated every six hours through 19 November. Until then, any listing’s own record is on its product page, and you can paste an AliExpress link to see what we hold for it.
Three windows, in UTC days:
A listing is compared only if we read it in both the “before” and the sale window and it is still listed. A listing whose readings are more than 3 times apart is left out: that is almost always a change of option (a different size, colour or bundle at a different price), not a sale. A difference of 1% or less counts as the same price.
We read listings in turn, so most are read every few days; a sale price we did not happen to read is not in these figures. Every price is the one AliExpress returned to us, in US dollars — the price at checkout, with shipping and your own coupons, can differ. The full method is on the methodology page.
Also worth checking: how much an AliExpress discount is really worth and every price we have recorded.