diff --git a/CHANGELOG.md b/CHANGELOG.md
index c4c2def14d..32a38be01e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,22 @@ However, because these polyfills create or extend global objects ('polluting the
 
 These changes were introduced in [pull request #1326: Remove IE11 vendor polyfills](https://github.com/nhsuk-frontend/pull/1326).
 
+#### Stop Internet Explorer 11 and other older browsers running unsupported JavaScript
+
+Add `type="module"` to all HTML `<script>` tags that include or bundle NHS.UK frontend.
+
+This is to stop Internet Explorer 11 and other older browsers running the JavaScript, which relies on features older browsers might not support and could cause errors.
+
+Please note that `<script>` with `type="module"` [runs JavaScript in a slightly different way](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules#other_differences_between_modules_and_standard_scripts) than `<script>` without `type="module". You'll need to assess the impact of these nuances and make sure that:
+
+- when your service code is bundled with NHS.UK frontend it runs as expected in [strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode)
+- if you have any code that needs to run after NHS.UK frontend in its own `<script>` tag, you'll need to make sure it's using `type="module"` or [`defer`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#defer). This is because the tag loading NHS.UK frontend will be deferred because of its `type="module"` attribute
+- code that needs to run without being deferred, is split into its own file and loaded with a `<script>` tag without `type="module"`
+
+If your service has JavaScript you want to run successfully in Internet Explorer (for example JavaScript for analytics), you will need to load it in a separate `<script>` tag without `type="module"` and make sure its code is compatible with the browsers it should run in (see previous section about polyfills).
+
+These changes were introduced in [pull request #1260: Remove legacy browser support with `<script type="module">`](https://github.com/nhsuk-frontend/pull/1260).
+
 #### Update header component params
 
 If you’re using the `header` Nunjucks macro in your service, you must:
diff --git a/app/_templates/layout.njk b/app/_templates/layout.njk
index 1f84aefef6..fd06458678 100644
--- a/app/_templates/layout.njk
+++ b/app/_templates/layout.njk
@@ -8,7 +8,7 @@
   <link href="https://assets.nhs.uk/fonts/FrutigerLTW01-55Roman.woff2" type="font/woff2" rel="preload" as="font" crossorigin>
   <link href="https://assets.nhs.uk/fonts/FrutigerLTW01-65Bold.woff2" type="font/woff2" rel="preload" as="font" crossorigin>
   <link href="{{ baseUrl }}stylesheets/nhsuk-{{ version }}.min.css" rel="stylesheet">
-  <script src="{{ baseUrl }}javascripts/nhsuk-{{ version }}.min.js" defer></script>
+  <script src="{{ baseUrl }}javascripts/nhsuk-{{ version }}.min.js" type="module"></script>
 {% endblock %}
 
 {# Turn the header and footer off #}
diff --git a/docs/installation/installing-compiled.md b/docs/installation/installing-compiled.md
index a01757abac..875f57b1e6 100644
--- a/docs/installation/installing-compiled.md
+++ b/docs/installation/installing-compiled.md
@@ -29,7 +29,7 @@ If you require any of this functionality, you should [install using npm](/docs/i
    <link rel="stylesheet" href="css/nhsuk-[latest version].min.css">
 
    <!-- Scripts -->
-   <script src="js/nhsuk-[latest version].min.js" defer></script>
+   <script src="js/nhsuk-[latest version].min.js" type="module"></script>
 
    <!-- Favicons -->
    <link rel="shortcut icon" href="assets/favicons/favicon.ico" type="image/x-icon">
diff --git a/docs/installation/installing-with-npm.md b/docs/installation/installing-with-npm.md
index 4ac4b42d19..4ffcfb74b7 100644
--- a/docs/installation/installing-with-npm.md
+++ b/docs/installation/installing-with-npm.md
@@ -79,19 +79,19 @@ document.body.className = ((document.body.className) ? document.body.className +
 
 ### Option 1: Include compiled JavaScript
 
-Include the `node_modules/nhsuk-frontend/dist/nhsuk.min.js` script in the `<head>` of your page using the `defer` attribute.
+Include the `node_modules/nhsuk-frontend/dist/nhsuk.min.js` script in the `<head>` of your page using the `type="module"` attribute.
 
-> The defer attribute is used for performance benefits as the browser loads the JavaScript file as soon as possible, due to it being in the `<head>`, but will not run until after the page has loaded.
+> The `type="module"` attribute stops Internet Explorer 11 and other older browsers running the JavaScript, which relies on features older browsers might not support and could cause errors. The script will be loaded as soon as possible, due to it being in the `<head>`, but will not run until after the page has loaded.
 
 You might wish to copy the file into your project or reference it straight from node_modules.
 
 ```html
-    <script src="path-to-assets/nhsuk.min.js" defer></script>
+    <script src="path-to-assets/nhsuk.min.js" type="module"></script>
   </head>
 ```
 
 ```html
-    <script src="node_modules/nhsuk-frontend/dist/nhsuk.min.js" defer></script>
+    <script src="node_modules/nhsuk-frontend/dist/nhsuk.min.js" type="module"></script>
   </head>
 ```