diff --git a/README.md b/README.md
new file mode 100644
index 0000000..9a64706
--- /dev/null
+++ b/README.md
@@ -0,0 +1,5 @@
+# `mb_trim`, `mb_ltrim`, and `mb_rtrim` polyfills
+
+Provides user-land PHP polyfills for the [`mb_trim`, `mb_ltrim`, and `mb_rtrim` functions added in PHP 8.4](https://php.watch/versions/8.4/mb_trim-mb_ltrim-mb_rtrim).
+
+Requires PHP 8.2 or PHP 8.3 with `mbstring` extension. Not supported on PHP 8.4 because these functions are natively implemented in PHP 8.4.