Stylesheets And JavaScript

Information on working with stylesheets and JavaScript in Umbraco, including bundling & minification.

Stylesheets in the Backoffice

You can create and edit stylesheets in the Stylesheets folder in the Settings section of the Backoffice.

Creating a new stylesheet

In the Create menu, these options are available:

  • Stylesheet file (for use in templates/views)

  • Rich Text Editor stylesheet file (for use in Rich Text Editor)

  • Folder (for keeping stylesheets organized)

It is currently not possible to use any CSS preprocessor (such as Syntactically Awesome Style Sheets (SASS)) in the backoffice.

After creating a new stylesheet, you would work with it as you would with templates or JavaScript files - using the built-in backoffice text editor. When you're working with stylesheets, you also have access to the Rich Text Editor, which allows you to create CSS styles and get a real-time preview.

Stylesheet Rich Text Editor (RTE)

The rules you create in the Rich Text Editor section will carry over to the Code tab.

Stylesheet RTE tab
Stylesheet Code tab

To reference your newly included stylesheet in a template file, navigate to Templates, pick the template you like (css files are usually referenced in the layout or home templates) and link to it with the link tag.

Linking CSS in template

By default, the stylesheets will be saved in the wwwroot/css folder in the solution. To reference them you can use either of the methods used in the above screenshot.

<link rel="stylesheet" href='@Url.Content("~/css/mystylesheet.css")' />


<link rel="stylesheet" href="/css/mystylesheet.css" />

With the stylesheet referenced, you will be able to style the template file with the rules and classes defined in the stylesheet.

Your stylesheets can be used in Rich Text Editors (datatype) as well - please see the Rich Text Editor documentation for more information.

If your RTE is styled differently on the frontend of the site, the backoffice styling might be getting overwritten by other stylesheets you have included.

JavaScript files in the Backoffice

To create and edit JavaScript files in the Backoffice, head on over to the Scripts folder in the Settings section of the Backoffice.

Creating a new JavaScript

From here you can add a new JavaScript file, or a new folder.

Add a new JavaScript file and write your code:

Sample JS script

Then, navigate to the template where you would like to include your JS file.

<script src="/scripts/myScript.js"></script>
Reference the script in template

By default all JavaScript files will be stored in the wwwroot/scripts folder in the solution.

If you are working locally, you can create CSS and JS files outside of the Backoffice - as long as they are placed in appropriate folders (css and scripts), they will show up in the Backoffice when you right-click on the folder and then pick reload.

Bundling & Minification for JavaScript and CSS

You can use whichever tool you are comfortable with for bundling & minification by implementing the IRuntimeMinifier interface in your custom minifier class, though it is worth noting that Umbraco 9+ ships with Smidge which offers lightweight runtime bundling and minification.

You can create various bundles of your site's CSS or JavaScript files in your code that can be rendered later in your views. There can be a single bundle for the entire site, or a common bundle for the files you want to be loaded on every page, as well as page-specific bundles, just by listing your resources in the order you like.

Smidge with RunTimeMinification setting is scheduled for removal on Umbraco 14. You can install the package separately if needed and read the Smidge documentation on how to get started.

Step 1: Create a INotificationHandler<UmbracoApplicationStartingNotification>

using Umbraco.Cms.Core;
using Umbraco.Cms.Core.Events;
using Umbraco.Cms.Core.Notifications;
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Core.WebAssets;

namespace Umbraco.Docs.Samples.Web.Stylesheets_Javascript;

public class CreateBundlesNotificationHandler : INotificationHandler<UmbracoApplicationStartingNotification>
    private readonly IRuntimeMinifier _runtimeMinifier;
    private readonly IRuntimeState _runtimeState;

    public CreateBundlesNotificationHandler(IRuntimeMinifier runtimeMinifier, IRuntimeState runtimeState) {
        _runtimeMinifier = runtimeMinifier;
        _runtimeState = runtimeState;
    public void Handle(UmbracoApplicationStartingNotification notification)
        if (_runtimeState.Level == RuntimeLevel.Run)
            new[] { "~/scripts/test-script1.js", "~/scripts/test-script2.js" });

                new[] { "~/css/test-style.css" });

See below for the different Bundling Options.

Step 2: Register the INotificationHandler in the Program.cs file.

    .AddNotificationHandler<UmbracoApplicationStartingNotification, CreateBundlesNotificationHandler>()

Step 3: Render the bundles by the bundle name in a view template file using the Smidge TagHelper:

    <script src="registered-js-bundle"></script>
    <link rel="stylesheet" href="registered-css-bundle"/>

Bundling Options

The following bundling options can be set when creating your bundles:

BundlingOptions.OptimizedAndComposite // The files will be minified and bundled into an individual file
BundlingOptions.OptimizedNotComposite // The files will be minified but not bundled into an individual file
BundlingOptions.NotOptimizedNotComposite // The files will not be minified and will not be bundled into an individual file
BundlingOptions.NotOptimizedAndComposite // The files will not be minified but will be bundled into an individual file


Using Smidge TagHelper

The Smidge TagHelper does not consider the value of Umbraco:CMS:Hosting:Debug set in your appsettings file.

If you do need to debug bundles you can inject hostingSettings and add the debug attribute as shown below.

@using Microsoft.Extensions.Options
@using Umbraco.Cms.Core.Configuration.Models
@inject IOptions<HostingSettings> hostingSettings
    var debugMode = hostingSettings.Value.Debug;
<script src="registered-js-bundle" debug="@debugMode"></script>
<link rel="stylesheet" href="registered-css-bundle" debug="@debugMode" />

Using IRuntimeMinifier

In case you are in Debug mode, your bundles won't be minified or bundled, so you would need to set Umbraco:CMS:Hosting:Debug: false in your appsettings file.

@using Umbraco.Cms.Core.WebAssets
@inject IRuntimeMinifier runtimeMinifier

    @Html.Raw(await runtimeMinifier.RenderJsHereAsync("registered-js-bundle"))
    @Html.Raw(await runtimeMinifier.RenderCssHereAsync("registered-css-bundle"))

Full details about Smidge can be found here:

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