How we build
every score
Every result on Beauty Dupe follows rules we set in advance. This page explains what data we use, what we count and what we deliberately leave out. For the story behind the service, see the about page.
Where does the ingredient data come from?
Every analysis starts from the full ingredient list. We gather it through three routes and verify all of them the same way.
Official brand listings
We regularly collect the full ingredient lists that brands publish on their official store pages. Korean cosmetics law requires sellers to display the full list on the product page, so the maker's own wording comes first.
Public INCI sources and user submissions
For overseas products we consult public INCI databases. Ingredient lists submitted by users on result pages are reviewed before they enter our data.
Cross-checked against the KFDA dictionary
Every collected name is checked against the public cosmetic ingredient database of the Korean Ministry of Food and Drug Safety. Lists that clash with the dictionary or contain text that is not an ingredient fail the automatic check and go to a person for review. Data verified by a person against the source is kept separate from data that passed automatic checks.
Why do we count shared ingredients instead of showing a percentage?
Ingredient lists do not disclose concentrations. A percentage score built without concentrations would suggest more certainty than the data supports, so we show what actually overlaps as a count. The same count can carry different weight, so actives that appear in more than one in ten products of our verified data are marked as widely used for context.
Base ingredients are not counted
Water, glycerin and butylene glycol appear in most products. Sharing them proves only that both products are moisturizers, so they never count toward a match.
Only actives that define the product count
Ingredients that decide what a product does, such as niacinamide, centella derivatives, ferment filtrates and peptides, are the ones we count as shared key ingredients. A common ingredient can still qualify when it sits near the top of both lists.
Fragrance and preservatives are checked, not counted
Fragrance and preservatives are handled as free-from checks rather than match evidence. Grounds for a match and points of caution are different questions.
How do we handle unknown concentrations?
Cosmetic labeling rules require ingredients above 1% to be listed in order of concentration. We use that rule to show whether each ingredient sits in the upper part of the list or in the estimated below-1% range. We state only what the order supports and never claim exact concentrations.
What separates a verified dupe from an AI estimate
Only pairs where we hold the full ingredient lists of both products and compared them directly are labeled verified dupes. When either list is missing, the AI estimates from public information and the result always carries the AI estimate label. The two labels are never mixed. Prices are checked against Naver Shopping market prices, and listings that are abnormally cheap or bundled are excluded from price verification.
How the skin-fit score works
A 16-question skin type test builds your skin profile, and analysis results are then reread against it.
Skin fit and avoid-list warnings
Helpful and caution ingredients are weighed by skin type to produce a fit score. If a product contains an ingredient on your avoid list, the same warning appears on every screen: dupe results, single analysis, comparison and routine.
Pregnancy and nursing preset
One button adds retinoids and similar caution ingredients to your avoid list. Only ingredient names are stored. Health information such as pregnancy status is never saved. This is a precautionary aid, so we always point to professional medical advice.
What this method cannot tell you
An ingredient list carries no texture, manufacturing process, raw material grade, exact concentration or skin feel. Products with similar compositions can still differ in finish, scent and how your skin reacts. Treat our results as a way to narrow candidates, and consult a professional for skin conditions or use during pregnancy and nursing.