diff --git a/lib/editor/tinymce/plugins/dragmath/dragmath.php b/lib/editor/tinymce/plugins/dragmath/dragmath.php
index e2b74dac64d..57ce3d9ac99 100644
--- a/lib/editor/tinymce/plugins/dragmath/dragmath.php
+++ b/lib/editor/tinymce/plugins/dragmath/dragmath.php
@@ -56,6 +56,7 @@ $relroot = preg_replace('|^http.?://[^/]+|', '', $CFG->wwwroot);
 
 $htmllang = get_html_lang();
 header('Content-Type: text/html; charset=utf-8');
+header('X-UA-Compatible: IE=edge');
 ?>
 <!DOCTYPE html>
 <html <?php echo $htmllang ?>
diff --git a/lib/editor/tinymce/plugins/loader.php b/lib/editor/tinymce/plugins/loader.php
index 7ca35ced624..071c48148f5 100644
--- a/lib/editor/tinymce/plugins/loader.php
+++ b/lib/editor/tinymce/plugins/loader.php
@@ -88,6 +88,8 @@ if ($mimetype === 'application/x-javascript' && $allowcache) {
     }
 
     $file = $cachefile;
+} else if ($mimetype === 'text/html') {
+    header('X-UA-Compatible: IE=edge');
 }
 
 // Serve file.
diff --git a/lib/editor/tinymce/plugins/moodleemoticon/dialog.php b/lib/editor/tinymce/plugins/moodleemoticon/dialog.php
index 39bf1ac9149..d26d8ebe24b 100644
--- a/lib/editor/tinymce/plugins/moodleemoticon/dialog.php
+++ b/lib/editor/tinymce/plugins/moodleemoticon/dialog.php
@@ -37,6 +37,7 @@ $plugin = $editor->get_plugin('moodleemoticon');
 
 $htmllang = get_html_lang();
 header('Content-Type: text/html; charset=utf-8');
+header('X-UA-Compatible: IE=edge');
 ?>
 <!DOCTYPE html>
 <html <?php echo $htmllang ?>
diff --git a/lib/installlib.php b/lib/installlib.php
index bc6f90223e0..7b8cca2c312 100644
--- a/lib/installlib.php
+++ b/lib/installlib.php
@@ -253,6 +253,7 @@ function install_print_help_page($help) {
     global $CFG, $OUTPUT; //TODO: MUST NOT USE $OUTPUT HERE!!!
 
     @header('Content-Type: text/html; charset=UTF-8');
+    @header('X-UA-Compatible: IE=edge');
     @header('Cache-Control: no-store, no-cache, must-revalidate');
     @header('Cache-Control: post-check=0, pre-check=0', false);
     @header('Pragma: no-cache');
@@ -299,6 +300,7 @@ function install_print_header($config, $stagename, $heading, $stagetext) {
     global $CFG;
 
     @header('Content-Type: text/html; charset=UTF-8');
+    @header('X-UA-Compatible: IE=edge');
     @header('Cache-Control: no-store, no-cache, must-revalidate');
     @header('Cache-Control: post-check=0, pre-check=0', false);
     @header('Pragma: no-cache');
diff --git a/lib/setup.php b/lib/setup.php
index 1e7c439ab95..90c5c73962e 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -182,6 +182,7 @@ if (defined('WEB_CRON_EMULATED_CLI')) {
 if (file_exists("$CFG->dataroot/climaintenance.html")) {
     if (!CLI_SCRIPT) {
         header('Content-type: text/html; charset=utf-8');
+        header('X-UA-Compatible: IE=edge');
         /// Headers to make it not cacheable and json
         header('Cache-Control: no-store, no-cache, must-revalidate');
         header('Cache-Control: post-check=0, pre-check=0', false);
diff --git a/lib/setuplib.php b/lib/setuplib.php
index ace9c430e91..33894adc14b 100644
--- a/lib/setuplib.php
+++ b/lib/setuplib.php
@@ -1540,6 +1540,7 @@ width: 80%; -moz-border-radius: 20px; padding: 15px">
 
         // better disable any caching
         @header('Content-Type: text/html; charset=utf-8');
+        @header('X-UA-Compatible: IE=edge');
         @header('Cache-Control: no-store, no-cache, must-revalidate');
         @header('Cache-Control: post-check=0, pre-check=0', false);
         @header('Pragma: no-cache');
diff --git a/lib/weblib.php b/lib/weblib.php
index 6be03c9b2dd..8bdf838c9bc 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -1849,6 +1849,10 @@ function send_headers($contenttype, $cacheable = true) {
     @header('Content-Script-Type: text/javascript');
     @header('Content-Style-Type: text/css');
 
+    if (empty($CFG->additionalhtmlhead) or stripos($CFG->additionalhtmlhead, 'X-UA-Compatible') === false) {
+        @header('X-UA-Compatible: IE=edge');
+    }
+
     if ($cacheable) {
         // Allow caching on "back" (but not on normal clicks)
         @header('Cache-Control: private, pre-check=0, post-check=0, max-age=0');