diff --git a/README.md b/README.md
index e7b2db4b..df0ea2a0 100644
--- a/README.md
+++ b/README.md
@@ -440,6 +440,12 @@ Here are a small sum-ups of the directory structure and their roles:
 - templates/: contain both html and email templates.
 - tests/: tests. We don't really distinguish unit, functional or integration test. A test is simply here to make sure a feature works correctly.
 
+The code is formatted using https://github.com/psf/black, to format the code, simply run
+
+```
+black
+```
+
 ### OAuth flow
 
 SL currently supports code and implicit flow.
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 00000000..2c4e6d78
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,18 @@
+[tool.black]
+exclude = '''
+(
+  /(
+      \.eggs         # exclude a few common directories in the
+    | \.git          # root of the project
+    | \.hg
+    | \.mypy_cache
+    | \.tox
+    | \.venv
+    | _build
+    | buck-out
+    | build
+    | dist
+    | migrations    # migrations/ is generated by alembic
+  )/
+)
+'''