Mathematicians value math's consistency and reliability. Formal proofs are exhaustively checked at foundational levels, typically by computers. Lean, developed by Leo de Moura at Microsoft in 2013, is the most popular proof assistant.
It has an open-source mathlib library with 300,000 theorems and 2.5 million lines of code. Autoformalization—formalizing math via AI—is becoming practical. In 2025-2026, milestones included Math Inc.'s quasi-autoformalization of the prime number theorem and J.
Urban's automatic formalization of 130k lines of topology in two weeks. Lean remains the leading tool for formalizing mathematics.
Source: Hacker News · Summarized by HeadlinesBriefing