Mathport is a tool for porting Lean3 projects to Lean4. It consists of two (loosely coupled) components:

  • "binport", which translates Lean3 .lean files to Lean4 .olean files
  • "synport", which best-effort translates Lean3 .lean files to Lean4 .lean files

Running on mathlib

If you want to port a file from mathlib to mathlib4, you don't need anything here. Instead you should go to the mathlib4 repository, and use scripts/

Running on a single file

Mathport supports a "oneshot" mode, for porting individual files or quick tests. A template is set up in the Oneshot/ directory. See Oneshot/

Running on a project other than mathlib

Install dependencies if needed:

  • debian/ubuntu: sudo apt install cmake jq gmp gmp-devel (possibly sudo apt install cmake jq libgmp3-dev instead)
  • mac: brew install cmake jq
  • On windows this script might not work

Get the mathport repo:

  • git clone

In the mathport folder:

  • lake exe cache get
  • make build This step is somewhat expensive as we need to compile (not just build) all of the dependencies of tactics.
  • make source
  • ./ (Or ./ [relevant-release] if you need to run against an old mathlib; see mathport releases, and find the nearest nightly.)

Make sure that your project is using the same version of Lean 3 as the latest mathlib3, if at all possible. Similarly bump your mathlib dependency to the lastest mathlib3 if possible.

If you really want to run against an older mathlib3 (good luck!):

  • In sources/mathlib run git fetch --unshallow
  • git checkout SHA for the mathlib3 SHA you need.
  • leanproject get-cache

Next, you'll need to prepare your project. It is probably best to clone a fresh copy for this (outside of the mathport directory).

In your project, run:

  • leanproject mk-all
  • make sure that leanproject build runs cleanly.
  • In leanpkg.path, change the line path _target/deps/mathlib/src to path ../mathport/sources/mathlib/src (this should be the relative path from your project to mathport's copy of mathlib/src.)
  • leanproject clean
  • lean --make --recursive --ast --tlean src (get coffee).

Now, in mathport, edit config-project.json as follows:

  • Under pathConfig/packages/, change the string after the "Project" key to the relative path from the mathport directory to your external project's src/ directory.

If you have used mathport on another project previously, you will need to rm -rf Outputs/oleans/project.

Then run

  • ./.lake/build/bin/mathport --make config-project.json Project::all

If it succeeds, you should find Lean4 lean files in Outputs/src/project/. (Note this may be hidden in the VS Code explorer, but you can open it in the terminal.)

If the generated Lean files look plausible, you will want to move them into a new Lean 4 project.

Somewhere outside of the mathport folder, run lake +leanprover/lean4:nightly-2023-05-22 init MyProject math (probably updating nightly-2023-05-22 to match the toolchain in current mathlib4). Then you can mv Outputs/src/project/Project ../MyProject/MyProject, and then inside MyProject run lake update and lake exe cache get.

You will need to edit the imports to change import Mathbin.XYZ to import Mathlib.XYZ.

Depending on the layout of your project, you may need to adjust imports or create secondary libraries in your lakefile.lean, e.g.

lean_lib ForMathlib where
  roots := #[`ForMathlib]

After that you should be able to edit files in VS Code, and begin fixing remaining errors.

Please expect errors if any of your filenames require escaping via «...». (In particular if your filenames start with numerals.)

Running with artifacts from continuous integration

A full run of mathport (see below) on Lean 3 and mathlib3 takes several hours. We provide artifacts on the github releases page, and separate repositories containing the .lean files and .olean files generated from Lean 3 and from mathlib3.

Please use the repositories and and run lake exe cache get and then lake build to obtain the generated .olean files.

Using these repositories, you can open the synported .lean files in VS Code to see the current state of output.

Alternatively, you can import some or all of the binported .olean files using e.g.

import Mathbin.AlgebraicGeometry.Scheme

#lookup3 algebraic_geometry.Scheme
#check AlgebraicGeometry.Scheme

(Specifying the mathlib3port repository as a Lake dependency in your own project should work to enable import Mathbin.All.)

Update 2022-10-21: The above binport configuration is no longer supported by default. The olean files generated by the nightlies now prioritize using the user specified alignments over type-correctness, so many mathlib theorems will be broken or stubbed. The old behavior can be recovered by setting "skipDefEq": false in the config.json, but you will have to run mathport yourself (see below) rather than downloading the pre-built artifacts created by make port.

The synported .lean files are checked in to these repositories: feel free to commit new versions if you have updated the dependencies in the relevant lakefile and downloaded fresh .lean files using the <tag> script, where <tag> is a release from

Running mathport locally

See the Makefile for usage (it takes several hours to rebuild the mathlib3 port from scratch). Basic usage is lake exe cache get and then make build source.

After that you can try just make predata port, but you probably should download artifacts first as described below.

We provide artifacts for various stages of the build on the releases page of the mathport repository. The script ./ nightly-YYYY-MM-DD downloads one of these, after which you can skip the make predata and/or make port steps (you will still need to run make build and make source).

The script ./ separately calls and We run CI for predata more frequently.

To port a single file execute mathport as follows (depending on whether you want to port a core or a mathlib file):

./.lake/build/bin/mathport config.json
./.lake/build/bin/mathport config.json Mathbin::field_theory.abel_ruffini

The directory Test contains subdirectories importLeanBin and importMathbin, each containing a lakefile.lean that depends on lean3port and mathlib3port, resp.