A JIT compiler—and its ecosystem—running entirely in the Web browser ​ Scientists, students, and engineers use Jupyter notebooks to explore ideas interactively: write a small piece of code, execute it, inspect the result, and continue from there. Traditionally, every such notebook requires a Python process running on a server or on the user's machine. JupyterLite changes this model. Its kernels run locally in the Web browser through WebAssembly, so a static website can provide a complete computational environment without allocating a server to every user. This makes notebooks easier and cheaper to share at scale, whether they are used for documentation, education, or interactive demonstrations. There has, however, been an important piece missing from the browser-based scientific Python ecosystem: Numba . Today, we are excited to share the first working version of the Numba JIT compiler running entirely in the browser with JupyterLite and emscripten-forge!…