diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..b47fa80
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,7 @@
+# Black version is kept in sync with .github/workflows/code_style.yml
+repos:
+  - repo: https://github.com/psf/black-pre-commit-mirror
+    rev: 26.1.0
+    hooks:
+      - id: black
+        args: ["--line-length=120"]
diff --git a/README.md b/README.md
index 7032d5a..09daa23 100644
--- a/README.md
+++ b/README.md
@@ -192,3 +192,15 @@ For running test do:
     pip install pytest pytest-cov coveralls
     pytest --cov-report html --cov=mergin mergin/test/
 ```
+
+### Code style
+
+Code is formatted with [black](https://github.com/psf/black) (line length 120), enforced in CI.
+To run the same check automatically before each commit, install the [pre-commit](https://pre-commit.com/) hooks once:
+
+```bash
+    pip install pre-commit
+    pre-commit install
+```
+
+The hook then runs on every `git commit`.