diff --git a/run.go b/run.go
index 4faa9751b..4ac482c68 100644
--- a/run.go
+++ b/run.go
@@ -166,9 +166,14 @@ func IsFullscreen() bool {
 // On fullscreen mode, the game screen is automatically enlarged
 // to fit with the monitor. The current scale value is ignored.
 //
-// Ebiten uses 'windowed' fullscreen mode, which doesn't change
+// On desktops, Ebiten uses 'windowed' fullscreen mode, which doesn't change
 // your monitor's resolution.
 //
+// On browsers, the game screen is resized to fit with the body element (client) size.
+// Additionally, the game screen is automatically resized when the body element is resized.
+//
+// SetFullscreen doesn't work on mobiles.
+//
 // This function is concurrent-safe.
 func SetFullscreen(fullscreen bool) {
 	ui.SetFullscreen(fullscreen)