We provide elementary insights into the effectiveness of certification to increase market transparency. In a market with opaque product quality, sellers use certification as a signaling device, while buyers use it as an inspection device. This difference alone implies that seller-certification yields more transparency and higher social welfare. Under buyer-certification profit maximizing certifiers further limit transparency, but because seller-certification yields larger profits, active regulation concerning the mode of certification is not needed. These findings are robust and widely applicable to, for instance, patents, automotive parts, and financial products.