The ID5 ID is a shared, neutral identifier that publishers and ad tech platforms can use to recognise users even in environments where 3rd party cookies are not available or blocked. ID5 enables publishers to create and distribute a shared 1st party identifier to the entire ecosystem. Ad tech platforms that connect with ID5 can decrypt the ID5 ID and improve their user recognition capabilities. The ID5 ID is designed to respect users' privacy choices throughout the advertising value chain.