Get your work checked

What this is

You send us your math. We check it with a computer. Then we send you a note that says what the computer found.

The note has a stamp with the time. It also says what we did not check. We will not say your idea is true if the computer did not check it.

What this is

Send us a Lean proof, or a written claim that rests on numbers. We run the same checker this site uses and send you a signed receipt with a timestamp.

The receipt lists what the machine checked and what it did not. A passing check means the proof was accepted by Lean, or the arithmetic adds up. It does not mean your statement says what you hoped it says, and we will tell you plainly where the gaps are.

What this is

Input: a Lean 4 file (Mathlib allowed), or a claim whose arithmetic can be restated as checkable steps. We compile it with the pinned toolchain the site uses, reject any file that uses sorry or adds axioms beyond the standard three, and record the axioms the result depends on.

Output: a receipt with the file hash, toolchain version, axiom list, verdict, a signature, and a Bitcoin timestamp. Scope limits are stated in the receipt: we verify that Lean accepts the proof of the statement as written. We do not certify that the formal statement matches your informal intent, and arithmetic checks cover only the steps you give us.

Price and how to pay

One check: $49 (GUESS, not final). Card fees take about $1.72, so we keep about $47.28 (REASONED from the guessed price and Stripe's posted fee).

Pay for one check (not live yet)

After you pay, email your file to [email protected] with your payment receipt. If the check cannot run at all, you get a full refund.

What we will never claim

We never call anything PROVEN unless a machine check passed with no sorry. Everything else on the receipt is labeled CHECKED, REASONED or GUESS.