PR0L1NESee your code run

Step through Python, JavaScript and TypeScript, and watch memory, loops and complexity change, right in your browser.

The memory view

Every variable, list, dict, object and scope as boxes and arrows, or nested inside one another. Linked lists come out as chains, trees as trees.

Each pass of a loop animated in place, or stacked under the last with arrows showing exactly what changed.

An estimate of time and space complexity from the code, checked against real runs at growing sizes.

viz: comments tell the canvas how to draw things when its own choices aren't what you want.

A link with your program inside it. Whoever opens it sees the code, ready to run in their browser's sandbox.

The tracers, the trace format, the sandbox and the renderers, step by step.