Is Wi-Fi Alliance certification mandatory?

Certification is not mandatory, and wireless products can be sold without certification. However, the Wi-Fi CERTIFIED trademark or text identifiers (such as Wi-Fi Protected Setup, Wi-Fi Direct, Miracast, etc...) cannot be used in market promotions, packaging, or product documentation. These CERTIFIED trademarks are owned by the Wi-Fi Alliance and require certification to be used on products. The Wi-Fi Alliance recommends certification to verify interoperability between wireless products.