diff --git a/pom.xml b/pom.xml
index e8c388a..1468345 100644
--- a/pom.xml
+++ b/pom.xml
@@ -157,6 +157,11 @@
       <artifactId>jstl</artifactId>
       <version>1.2</version>
     </dependency>
+    <dependency>
+      <groupId>org.webjars</groupId>
+      <artifactId>codemirror</artifactId>
+      <version>3.21</version>
+    </dependency>
     <dependency>
       <groupId>HTTPClient</groupId>
       <artifactId>HTTPClient</artifactId>
diff --git a/src/main/webapp/index.jsp b/src/main/webapp/index.jsp
index bd41ffe..93d9ace 100644
--- a/src/main/webapp/index.jsp
+++ b/src/main/webapp/index.jsp
@@ -23,9 +23,11 @@
     <meta http-equiv="expires" content="0" />
     <meta http-equiv="pragma" content="no-cache" />
     <meta http-equiv="cache-control" content="no-cache, must-revalidate" />
-    <link rel="stylesheet" href="${contextroot}/plantuml.css" type="text/css"/>
     <link rel="icon" href="${contextroot}/favicon.ico" type="image/x-icon"/> 
     <link rel="shortcut icon" href="${contextroot}/favicon.ico" type="image/x-icon"/>
+    <link rel="stylesheet" href="${contextroot}/plantuml.css" />
+    <link rel="stylesheet" href="webjars/codemirror/3.21/lib/codemirror.css" />
+    <script src="webjars/codemirror/3.21/lib/codemirror.js"></script>
     <title>PlantUMLServer</title>
 </head>
 <body>
@@ -41,7 +43,7 @@
     <%-- CONTENT --%>
     <form method="post" accept-charset="UTF-8"  action="${contextroot}/form">
         <p>
-            <textarea name="text" cols="120" rows="10"><c:out value="${decoded}"/></textarea>
+            <textarea id="diagtext" name="text" cols="120" rows="10"><c:out value="${decoded}"/></textarea>
             <br/>
             <input type="submit" />
         </p>
@@ -82,5 +84,8 @@
 </div>
 <%-- FOOTER --%>
 <%@ include file="footer.jspf" %> 
+<script>
+    var myCodeMirror = CodeMirror.fromTextArea(document.getElementById("diagtext"), {lineNumbers: true});
+</script>
 </body>
 </html>
