The Sapin Law, adopted on January 29, 1993, is French legislation designed to guarantee transparency and fairness in the purchase of advertising space. It mandates the publication of pricing terms and the sending of a detailed invoice directly to the advertiser, even when payment is made through a media agency. This law combats corruption by prohibiting hidden payments to intermediaries and requires a formal contract between the advertiser and the media agency. Since January 1, 2018, its scope has also extended to online advertising.