diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4aaa0ad
--- /dev/null
+++ b/README.md
@@ -0,0 +1,18 @@
+# Scratch Everywhere! Native Extensions
+
+A collection of _native_ extensions for Scratch Everywhere!.
+
+> [!WARNING]
+> Custom extensions in Scratch Everywhere! are still in development. Native
+> extensions currently only work on **macOS** and **Linux**.
+
+# Building
+
+Building native extensions is the exact same process as building Scratch
+Everywhere! normally. In order for a native extension to work on Scratch
+Everywhere!, it must be built on the **same system**, using the **same
+compiler** and the **same arguments**, with the **same version of Scratch
+Everywhere!**.
+
+Instructions for building Scratch Everywhere! can be found on the
+[website](https://scratcheverywhere.github.io/build).