diff --git a/README.md b/README.md
index 51004ac..b9847e1 100644
--- a/README.md
+++ b/README.md
@@ -21,4 +21,8 @@ Then edit manually `config.js`.
 node traque.js
 ```
 
-Then visit `localhost:9000`.
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+Then visit `localhost:9000`.
+
+## About certificates
+
+For testing purpose, a self-signed certificate (and the associated private key) is present in the `certif` directory. It should **not** be used for anything but testing. The default `sample_config.js` uses this certificate.
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