Cert is a UK car-market research service that helps buyers assess whether a used-car listing is fairly priced. Users can paste a listing link from platforms such as Autotrader, Gumtree, CarGurus, cinch, Facebook Marketplace, or dealer websites and receive an estimate based on comparable live adverts, alongside available vehicle-history information and recorded flags. Checking a listing is free and does not require an account.

Cert compares cars by factors including model, mileage, and year, and presents pricing in context so buyers can see whether an asking price appears below, within, or above the estimated fair range. Its estimates are modelled from asking prices collected monthly from public Autotrader listings using quantile regression; Cert notes that these are estimates, not formal valuations, and advises buyers to inspect vehicles before purchasing.

The service also offers Cert Deals, a browseable selection of listings, and tools for finding a desired car. Users can describe their budget and requirements, save cars and searches in a personal dashboard, and receive email alerts when a matching vehicle appears below fair value. Cert covers cars and also points users to markets for vans and bikes.