Meridian

Google-backed open-source MMM framework competing with Meta's Robyn and commercial MMM vendors, positioned as the privacy-safe measurement standard for the post-cookie era

Meridian is Google's open-source marketing mix modeling (MMM) framework, released publicly in 2024 to help marketers and data scientists measure the causal impact of advertising spend across channels. Built on a Bayesian statistical foundation using Python and Stan, Meridian enables brands to quantify return on ad spend (ROAS), optimize budget allocation, and understand media saturation and diminishing returns — all without requiring user-level tracking data. It is designed to complement Google's existing measurement ecosystem, including tools like Robyn (Meta's competing open-source MMM) and proprietary attribution platforms. Meridian addresses growing industry demand for privacy-safe, aggregate-level measurement as third-party cookies are deprecated and signal loss accelerates across the digital advertising landscape. By open-sourcing the framework, Google positions itself as a trusted measurement partner while encouraging adoption of a methodology that naturally incorporates Google media data. The tool supports geo-level modeling, prior calibration with incrementality experiments, and flexible media transformations such as adstock and Hill saturation curves. In the AdTech ecosystem, Meridian competes with Meta's Robyn, Lightweight MMM (from Google's own PyMC Marketing contributors), and commercial MMM vendors such as Analytic Partners, Nielsen, and Ekimetrics. Its significance lies in democratizing sophisticated econometric modeling for brands of all sizes, reducing reliance on black-box attribution, and providing a transparent, auditable methodology that regulators and privacy advocates increasingly favor.