Lantern

Lantern is an explainer engine that renders animated, steppable code visualizations to SVG with step links, plain-text frames, and JSON state traces.

Lantern creates animated, steppable explainers for code. Each scene consists of a sequence of named steps containing an SVG frame, a plain-text frame, and a JSON trace of the underlying state. It runs via a zero-dependency engine directly in web pages or in a background Worker. Users can step through sequences, pause on each step, or navigate using a timeline whose URL parameters update dynamically. Developers can author scenes as classes or declare them as JSON documents containing nodes, edges, code, and step operations. Every scene is accessible via an open HTTP GET API without authentication.

Lantern at a glance

Best for: Software engineer
Runs on: Web, API
Pricing: Free
Released: October 2026
Category: AI coding tool
Website: lantern.ivar.workers.dev

Key features

Steppable playback with play, pause, and per-step pause modes
Timeline seeking and step-list jumping with dynamic URL syncing
Deep linking by scene name, step name, or timestamp
Zero-dependency rendering engine outputting directly to SVG
HTTP GET API for fetching frames as SVG, text, or JSON traces
Configurable SVG export widths via URL parameters
Scene authoring via JavaScript/TypeScript classes or JSON documents
Plain-text agent guides available at root and /llms.txt

Use it for

Stepping through code execution and state changes visually
Embedding specific SVG or text animation frames into external tools via HTTP
Sharing links to exact frames or timestamps in a code explanation
Generating JSON traces of program state transitions across steps

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