Lean web editor https://live.lean-lang.org/
  • TypeScript 75%
  • JavaScript 11.1%
  • CSS 9.3%
  • Lean 2%
  • Shell 2%
  • Other 0.6%
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2026-06-28 00:15:47 +02:00
.github/workflows chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
.vscode chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
client chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
cypress chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
doc feat: add setting to set a ruler (#125) 2026-06-27 21:43:50 +02:00
Projects chore: bump npm dependencies (#126) 2026-06-27 22:23:39 +02:00
server chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
.editorconfig prettier & tailwind (#84) 2025-12-28 16:52:56 +01:00
.gitignore Validate project files, add order, insert version (#122) 2026-06-27 20:23:55 +02:00
.npmrc Add cypress (#57) 2025-03-07 17:02:09 +01:00
cypress.config.ts chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
ecosystem.config.cjs chore: enable autoformatting with oxfmt (#129) 2026-06-28 00:15:47 +02:00
LICENSE add license 2023-08-28 14:46:24 +02:00
oxfmt.config.ts chore: replace eslint and prettier with oxlint and oxfmt (#128) 2026-06-28 00:13:37 +02:00
oxlint.config.ts chore: replace eslint and prettier with oxlint and oxfmt (#128) 2026-06-28 00:13:37 +02:00
package-lock.json chore: replace eslint and prettier with oxlint and oxfmt (#128) 2026-06-28 00:13:37 +02:00
package.json chore: replace eslint and prettier with oxlint and oxfmt (#128) 2026-06-28 00:13:37 +02:00
README.md feat: more reactive navigation; update Logo (#119) 2026-06-27 18:46:36 +02:00
SECURITY.md Add security policy (#93) 2026-03-14 12:18:32 +01:00

GitHub license ci status

Lean Web

This is a web application running Lean 4 server-side. There is a playground hosted at live.lean-lang.org and one at lean.math.hhu.de.

In contrast to the Lean 3 web editor, in this web editor, the Lean server is running on a web server, and not in the browser.

Scope of Lean Web

  • Minimalistic and accessible way to run some (smallish) Lean snippets
  • Run MWEs from Zulip with the latest Mathlib installed.
  • Demonstrate some Lean code in talks/lecutres.
  • Doodling around with Lean before installing it as a newcomer.
  • Run some Lean code in a mobile context.

Currently, serious Lean code development and larger projects are considered out-of-scope. For these, it might be more suitable to look at a setup using Codespaces or Gitpot.

While lean4web looks very similar to VSCode with the Lean4 extension installed - and it reuses much of that code - lean4web does not claim to be feature complete.

Contribution

If you experience any problems, or have feature requests, please open an issue here!

PRs fixing issues are very welcome!

Regarding new features, it's best to write an issue first to discuss them: For example, some functionality might be better implemented in lean4monaco which provides the key features and a discussion might be helpful to figure this out.

Documentation