In markets with quality unobservable to buyers, third-party certification is often the only instrument to increase transparency. While both sellers and buyers have a demand for certification, its role differs fundamentally: sellers use it for signalling, buyers use it for inspection. Seller-induced certification leads to more transparency, because it is informative—even if unused. By contrast, buyer-induced certification incentivizes certifiers to limit transparency, as this raises demand for inspection. Whenever transparency is socially beneficial, seller certification is preferable. It also yields certifiers larger profits, so that regulating the mode of certification is redundant.