Most marketing mix modeling tools fall into two categories: enterprise platforms that cost $50k or more per year, and open-source frameworks that require a data scientist to operate. This post covers the main free options, what they actually require to run, and who each one is realistically for. (New to MMM? Start with our complete guide to marketing mix modeling.)
Meta Robyn
Robyn is Meta's open-source MMM package, built in R. It handles adstock transformations, saturation modeling, and uses Nevergrad optimization to produce Pareto-optimal model selections. The methodology is solid and the community is active.
The practical barrier is R itself. Setting up Robyn means installing R, configuring environment variables, resolving package dependencies including a Python bridge for Nevergrad, and writing scripts to prepare your data. For someone without an R background, the setup alone can take a full day before any modeling happens.
Robyn is a good choice for data scientists or analysts who already work in R and want a rigorous, configurable MMM framework. It is not realistic for marketing teams without that background.
Google Meridian
Meridian is Google's Bayesian MMM framework, built in Python using PyMC. It incorporates reach and frequency data, supports prior-informed modeling, and integrates naturally with Google Ads data. Google released it globally in early 2025 and has updated it actively since.
The setup requires Python, JAX, PyMC, and familiarity with Jupyter notebooks. Bayesian modeling also has a learning curve beyond just the tooling — understanding how to set priors and interpret posterior distributions takes time. Google's documentation is thorough but assumes statistical fluency.
Meridian is well-suited for Python-proficient analysts, particularly those working within the Google advertising ecosystem. Teams without that infrastructure will find the setup significant.
PyMC-Marketing
PyMC-Marketing is the most academically rigorous open-source option. It offers full Bayesian inference with MCMC sampling, custom priors, and posterior analysis. The documentation is strong and the library is under active development.
It requires the same Python and PyMC stack as Meridian, plus comfort with Bayesian modeling concepts. It is primarily aimed at data scientists who want full control over model specification.
Google LightweightMMM
LightweightMMM was Google's earlier open-source MMM library, built on NumPyro. It has been officially deprecated in favor of Meridian. If you find tutorials referencing it, note that it is no longer maintained.
CheapMMM
CheapMMM runs entirely in the browser. Upload a CSV with date, sales, and per-channel spend columns and get ROAS by channel, feature importance scores, carryover insights, and a budget optimizer. No installation, no code, no login.
The model uses geometric adstock transformations to capture delayed media effects, Hill-function saturation curves for diminishing returns, and a Gradient Boosting Regressor as the core estimator. Hyperparameters are tuned via grid search across both the structural marketing parameters and model complexity. Attribution uses SHAP values where available.
The outputs are directional. CheapMMM is not a replacement for geo holdout experiments or randomized incrementality testing. It is designed for teams that need a fast, structured read on channel performance before a budget decision, without the setup overhead of the open-source frameworks above.
Works best with at least 6 months of weekly or monthly data and reasonable spend variation across channels.
Which one is right for you
If you have a data science team comfortable in R or Python, Robyn or Meridian will give you more modeling control and configurability. If you want Bayesian uncertainty quantification, PyMC-Marketing is the most capable option in that category.
If you need results today without engineering support, CheapMMM is the only option on this list that requires nothing beyond a spreadsheet.