diff --git a/index.html b/index.html
index e944ff5dbe8dcd4b220e1de246780a32916d856e..197c0933fd850add493b3211c867bef7e52e5a0f 100644
--- a/index.html
+++ b/index.html
@@ -12,6 +12,7 @@
 <body style="background-color: rgb(255, 255, 255);">
 	<h1>gerber2img</h1>
 	<p>Drag and drop one or multiple Gerber files; lock origin and dimensions to preserve alignment between successive uploads.</p>
+	<p>For through-holes and vias, make sure to export drill file (.drl) as metric.</p>
 	<div id="dropZone"><p id="dropText">↑</p></div>
 	<input type="file" id="fileInput" multiple hidden></input>
 	<canvas id="canvas" hidden></canvas>