marimo

marimo is a San Francisco company building an open-source reactive Python notebook that replaces the error-prone JSON of Jupyter with pure Python files. Cells form a dataflow graph, so changing one variable automatically re-runs the cells that depend on it - notebooks are reproducible, git-friendly, deployable as apps, executable as scripts, and can even run entirely in the browser via WebAssembly. Founded in 2022 by Akshay Agrawal and Myles Scolnick, marimo raised a $5M seed in 2024 and joined CoreWeave in October 2025 while keeping the notebook free and permissively licensed.