diff --git a/administrator/templates/isis/css/template-rtl.css b/administrator/templates/isis/css/template-rtl.css
index 7ba0c76e86fa1..b8615fbefca84 100644
--- a/administrator/templates/isis/css/template-rtl.css
+++ b/administrator/templates/isis/css/template-rtl.css
@@ -3911,12 +3911,13 @@ input[type="submit"].btn.btn-mini {
 .modal-body {
 	width: 98%;
 	position: relative;
-	max-height: 400px;
+	max-height: none;
 	padding: 1%;
 }
 .modal-body iframe {
 	width: 100%;
 	max-height: none;
+	height: 70vh;
 	border: 0 !important;
 }
 .modal-form {
@@ -6221,6 +6222,7 @@ div.modal.fade {
 }
 div.modal.fade.in {
 	top: 5%;
+	top: 5vh;
 }
 .modal-batch {
 	overflow-y: visible;
@@ -6239,6 +6241,10 @@ div.modal.fade.in {
 	}
 	div.modal.fade.in {
 		top: 20px;
+		top: 2vh;
+	}
+	.modal-body {
+		height: 79vh;
 	}
 }
 @media (max-width: 480px) {
diff --git a/administrator/templates/isis/css/template.css b/administrator/templates/isis/css/template.css
index eedd9f67d71c1..899feddc819d4 100644
--- a/administrator/templates/isis/css/template.css
+++ b/administrator/templates/isis/css/template.css
@@ -3911,12 +3911,13 @@ input[type="submit"].btn.btn-mini {
 .modal-body {
 	width: 98%;
 	position: relative;
-	max-height: 400px;
+	max-height: none;
 	padding: 1%;
 }
 .modal-body iframe {
 	width: 100%;
 	max-height: none;
+	height: 70vh;
 	border: 0 !important;
 }
 .modal-form {
@@ -6221,6 +6222,7 @@ div.modal.fade {
 }
 div.modal.fade.in {
 	top: 5%;
+	top: 5vh;
 }
 .modal-batch {
 	overflow-y: visible;
@@ -6239,6 +6241,10 @@ div.modal.fade.in {
 	}
 	div.modal.fade.in {
 		top: 20px;
+		top: 2vh;
+	}
+	.modal-body {
+		height: 79vh;
 	}
 }
 @media (max-width: 480px) {
diff --git a/media/jui/less/modals.joomla.less b/media/jui/less/modals.joomla.less
index 492f92b666e77..46778d7e795c2 100644
--- a/media/jui/less/modals.joomla.less
+++ b/media/jui/less/modals.joomla.less
@@ -27,7 +27,10 @@ div.modal {
     .transition(e('opacity .3s linear, top .3s ease-out'));
     top: -25%;
   }
-  &.fade.in { top: 5%; }
+  &.fade.in {
+    top: 5%; // for old browser without Viewport height(vh)-Support
+    top: 5vh;
+  }
 }
 //Modal for Batch views
 .modal-batch {
diff --git a/media/jui/less/modals.less b/media/jui/less/modals.less
index 0932e0c8871e6..4291e1543c9d3 100644
--- a/media/jui/less/modals.less
+++ b/media/jui/less/modals.less
@@ -41,13 +41,14 @@
 .modal-body {
   width: 98%;
   position: relative;
-  max-height: 400px;
+  max-height: none;
   padding: 1%;
 }
 // Remove border and scrollbar from iframe modal
 .modal-body iframe {
   width: 100%;
   max-height: none;
+  height: 70vh; //overrides browser standard (300px)
   border: 0 !important;
 }
 // Remove bottom margin if need be
diff --git a/media/jui/less/responsive-767px-max.joomla.less b/media/jui/less/responsive-767px-max.joomla.less
index d8ff8f7e97626..126ae992e9ad6 100644
--- a/media/jui/less/responsive-767px-max.joomla.less
+++ b/media/jui/less/responsive-767px-max.joomla.less
@@ -16,7 +16,14 @@
     width: auto;
     margin: 0;
     &.fade  { top: -100px; }
-    &.fade.in { top: 20px; }
+    &.fade.in {
+      top: 20px;
+      top: 2vh;
+    }
+  }
+
+  .modal-body {
+    height: 79vh;
   }
 
 }
diff --git a/templates/protostar/css/template.css b/templates/protostar/css/template.css
index 1d766ed920f84..6754fe61cdf50 100644
--- a/templates/protostar/css/template.css
+++ b/templates/protostar/css/template.css
@@ -3926,12 +3926,13 @@ input[type="submit"].btn.btn-mini {
 .modal-body {
 	width: 98%;
 	position: relative;
-	max-height: 400px;
+	max-height: none;
 	padding: 1%;
 }
 .modal-body iframe {
 	width: 100%;
 	max-height: none;
+	height: 70vh;
 	border: 0 !important;
 }
 .modal-form {
@@ -6207,6 +6208,7 @@ div.modal.fade {
 }
 div.modal.fade.in {
 	top: 5%;
+	top: 5vh;
 }
 .modal-batch {
 	overflow-y: visible;
@@ -6225,6 +6227,10 @@ div.modal.fade.in {
 	}
 	div.modal.fade.in {
 		top: 20px;
+		top: 2vh;
+	}
+	.modal-body {
+		height: 79vh;
 	}
 }
 @media (max-width: 480px) {