Terms of Use

Last updated: September 12, 2026

Educational content

Lean 4 Dev publishes educational content about Lean 4 programming and theorem proving. The material is provided for learning and reference. It is not a substitute for official Lean documentation, professional software review, or academic advice.

Academy subscriptions and compiler use

The Academy pricing page describes the courses, price, billing interval, and compiler allowances included in each plan. Pro renews monthly until canceled. You can manage payment details and cancel renewal through My account. Canceling renewal preserves access until the end of the current paid period.

A compiler check is a single submitted run, including runs that find errors in the submitted code. Personal allowances reset at the start of each calendar month in UTC and do not roll over. Checks are subject to execution, memory, source-size, and shared capacity limits shown on the pricing page. These limits help keep the service available and affordable.

The playground is for small educational programs and proofs. It is not a persistent server or a general hosting service. Do not attempt to evade usage limits, access another user’s data, or interfere with the service. A successful compilation with an unfinished proof warning does not establish that the proof is complete.

Contact contact@lean4.dev for billing errors, refund requests, or service problems. These terms do not restrict consumer rights that apply by law. A preview explicitly labeled Stripe test mode does not accept real payments.

Acceptable use

• Use the site for learning, teaching, and research.
• Do not attempt to disrupt, scrape abusively, or attack the site.
• Do not submit malicious code, spam, or private credentials through contact channels.

Accuracy

Lean and Mathlib change over time. The site aims to keep examples useful, but code snippets may need adjustment for future Lean or Mathlib versions. Corrections can be sent through the contact page.

Intellectual property

The Lean name, Lean project, and Mathlib belong to their respective communities and rights holders. Lean 4 Dev is independent and is not officially affiliated with the Lean FRO.

Code examples on the site are intended for learning and adaptation unless a specific page states otherwise.

Advertising

The site may display advertising to support hosting and maintenance. Advertising does not imply endorsement by Lean 4 Dev, and editorial content is not controlled by advertisers.

No warranty

The site is provided on an as-is and as-available basis. Lean 4 Dev does not warrant that every example will be error-free, uninterrupted, or suitable for every use case.

Contact

Questions about these terms can be sent to contact@lean4.dev.

See also the Privacy Policy and Editorial Policy.