Walled gardens refer to closed ecosystems on the web owned and controlled by a single company, such as Facebook, Amazon, and Google. Advertisers in walled gardens can only reach users within that ecosystem. For example, when a brand advertises on Facebook, the ad is only shown to people who have a Facebook account and are actively on the platform.
Walled gardens typically have vast amounts of user data, and offer sophisticated ad targeting and measurement tools for advertisers. While walled gardens provide advertisers with efficient access to a large audience, they have significant downsides. Unlike the open web, walled gardens limit competition and transparency, which can drive up advertising costs, and give advertisers less control over ad placements. In addition, walled gardens consolidate market power, leading to a more centralized digital advertising landscape, which is detrimental to the integrity and sustainability of journalism today.