Basics
Walled garden
A walled garden is a large platform, such as Google, Meta, Amazon or TikTok, that controls its own users, data, ad sales and measurement inside a closed ecosystem.
A walled garden keeps everything in-house. Advertisers who want to reach its users must buy through its own tools, use its own targeting data, and mostly rely on its own reporting. Classic examples are Meta (Facebook, Instagram), Google Search and YouTube, Amazon, TikTok, Snap and, increasingly, big retail media networks and streaming platforms.
Walled gardens are attractive because they have vast logged-in audiences and rich first-party data, which enables precise targeting and closed-loop measurement. They are also convenient: one self-serve platform interface covers planning, buying and reporting.
The downsides are control and transparency. Advertisers cannot easily take the data out, independent ad verification is limited, and the platform "grades its own homework" on results. Data sharing typically happens through clean rooms rather than raw logs. Regulators have examined walled gardens under antitrust in ad tech law and rules like the EU's Digital Markets Act, which labels the largest as gatekeepers.
Think of it like this
A walled garden is like a theme park: everything inside is well run and convenient, but you must use its tickets, eat its food and trust its own count of how much fun you had.
An example
A mobile game studio spends 70% of its budget on Meta and Google because their in-platform audiences and optimisation deliver installs at scale, and 30% on the open web through mediation networks.
Related terms
Open web
The open web is the part of the internet outside the big closed platforms, such as independent websites, apps and streaming services, where ads are bought through shared, interoperable ad tech.
First-party data
First-party data is information a company collects directly from its own customers or audience, such as purchases, sign-ups, app use and site behaviour, through its own channels.
Data clean room
A data clean room is a secure environment where companies combine and analyse their customer data together, getting aggregated insights or audiences without exposing each other's raw personal data.
Paid social
Paid social is advertising on social media platforms, such as Facebook, Instagram, TikTok, YouTube, LinkedIn, Snapchat, Pinterest and X, where ads appear in feeds, stories and short videos.
Digital Markets Act (DMA)
The Digital Markets Act (DMA) is an EU regulation imposing competition-style obligations on designated "gatekeeper" tech platforms, including limits on combining personal data for ads without consent.