diff --git a/readme.md b/readme.md
index 02be405..8b07920 100644
--- a/readme.md
+++ b/readme.md
@@ -38,6 +38,12 @@ This setup has a lot of impurities, for one firefox with aboslute paths and for
 | mod4 + t   | start terminal (alacritty) |
 | mod4 + r   | start firefox              |
 
+# compositor
+
+| key-stroke | command                                    |
+| ---------- | ------------------------------------------ |
+| mod4 + o   | toggle opacity of currently focused window |
+
 # languages
 
 | key-stroke | command      |