diff --git a/hardware/physical-web/physical-web.html b/hardware/physical-web/physical-web.html
index 66aabf89..24237171 100644
--- a/hardware/physical-web/physical-web.html
+++ b/hardware/physical-web/physical-web.html
@@ -97,6 +97,7 @@
     <div class="form-row">
         <label for="node-input-url"><i class="fa fa-link"></i> URL</label>
         <input type="text" id="node-input-url" placeholder="http://...">
+        <p>This URL needs to be shorter than 18 bytes in length</p>
     </div>
     <br/>
     <div class="form-row">