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Client resources

Explains how to define and configure available client resources.

You can do this through the EPiServer.Framework.Web.Resources.ClientResource class and interfaces, to render or inject client resources into content without modifying the templates.

Define client resource definitions in module.config

The client resource provider finds and returns definitions of client resources, defined in manifests of public and protected modules and add-ons. You can request the definition by name and add it to the page. You do not need a custom client resource provider if you define the resources in module.config. The following example shows client resource definitions in a module manifest:

<?xml version="1.0" encoding="utf-8" ?>
		<add name="epi.samples.Module.Styles" path="ClientResources/Styles.css" resourceType="Style"/>

Implement the custom client resource provider

The client provider class must implement the EPiServer.Framework.Web.Resources.IClientResourceProvider interface, and it should be decorated with EPiServer.Framework.Web.Resources.ClientResourceProviderAttribute to register this implementation automatically. In the following example, the sample client resource provider returns one script resource that depends on another client resource provider. The provider resolves the full path to the script file in the module directory by module name.

public class ClientResourceProvider: IClientResourceProvider {
  public IEnumerable<ClientResource> GetClientResources() {
    return new [] {
      new ClientResource {
        Name = "epi.samples.Module.FormHandler",
          Path = Paths.ToClientResource("SampleModuleName", "ClientResources/FormHandler.js"),
          ResourceType = ClientResourceType.Script,
          Dependencies = new List<string> {

Requiring client resources

You can require client resources (often when developing an add-on or plug-in) to render on the page without accessing and changing page templates.

Implementing client resource register

Optimizely Content Management System (CMS) provides the EPiServer.Framework.Web.Resources.IClientResourceRegistrator interface that can be implemented to register client resources for specific rendering areas and depends on the current context.

You must execute client resource registers before rendering a page. The code calls register automatically if templates inherit base classes for Razor pages or controllers that are defined in CMS (EPiServer.Web.Mvc.RazorPageModel and EPiServer.Web.Mvc.ContentController). Also, when you request resources for CMS page templates, the resources can inherit the base register class. You should decorate the register implementation class with EPiServer.Framework.Web.Resources.RequireClientResourcesAttribute to make it discoverable automatically.

In the following code example,

  • RegisterResources method takes one argument: the list of required client resources.
  • Information from the current HTTP context can decide which resources are required for this context. An implementation that needs access to the current HTTP context should take a dependency on Microsoft.AspNetCore.Http.IHttpContextAccessor.
  • The list of required client resources provides the number of Require methods to register required client resources.
  • You can require a client resource by name if it is known and defined in any module manifest, or a custom resource provider returns it. The example register requires two resources by name, defined in the sample module manifest and sample client resource provider.
public class ClientResourceRegister: IClientResourceRegistrator {
  public void RegisterResources(IRequiredClientResourceList requiredResources) {



The third resource was not defined in module.config or provider and this resource is required using its URL in sample register implementation.

You can require JavaScript, CSS, or HTML resources by specifying the URL or inline content you should inject on the page.

See also: EPiServer.Framework.Web.Resources.IRequiredClientResourceList members.

Client resource settings

Each Require method returns settings for required client resources to specify an area where you render a resource and filter resources by type.

Render area

This string identifies the place in templates where you render a resource.

Optimizely requires two default rendering areas for all templates:

  • Header for resources you should add inside the <head> tag. You should require styles for this area.
  • Footer for resources that you should add at the bottom of the page, before closing </body> tag. You should put scripts in this area.

You can set the rendering area for a resource by using AtArea(areaName), AtHeader(), AtFooter() methods of client resource settings.

If you do not specify the rendering area explicitly, the Header is the default option. The sample register requires a style resource without setting the area so that this style is rendered in the Header area. Footer area explicitly requires two other script resources.

Filter Resources by Type

Sometimes several resources of different types are grouped and have the same name. You can request only resources of a certain type when you request resources by name. For example, you can define jQuery UI scripts and CSS files using the one name jquery.ui. Then require jQuery UI style resource in the Header area and require scripts in the Footer:


Request client resources using ClientResources class

Client resource register requires implementation when you develop a module and add-on that needs injections.

You can require client resources by using the EPiServer.Framework.Web.Resources.ClientResources static class, which provides Require methods with the same signatures as methods in IRequiredClientResourceList interface, if you must request client resources in code behind or templates. Request resources before you render the required resources for the corresponding area.

Render the required client resources

Use HTML helper to render required client resources for a corresponding area. A template must render required client resources at least for two default areas. Render resources for the Header area inside <head> tag. Render resources for Footer area at the bottom of the page, before closing </body> tag.

MVC Helper

Use HTML helper extension to render required resources in MVC templates. The following code renders client resources required for the Footer area: