diff --git a/web/index.ejs b/web/index.ejs
index b4623f2..e635ed2 100644
--- a/web/index.ejs
+++ b/web/index.ejs
@@ -308,7 +308,7 @@
                 <div style="display:inline-block">
                     <span style="margin-left: 20px;display: block;margin-top: 2px;" class="data-flag"></span>
                 </div>
-                <span class="pointer stereo-container" style="position: relative; margin-left: 20px;">
+                <span class="pointer stereo-container" style="position: relative; margin-left: 20px;" role="button" aria-label="Stereo / Mono toggle" tabindex="0">
                     <div class="circle-container">
                         <div class="circle data-st circle1"></div>
                         <div class="circle data-st circle2"></div>