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Custom Themes

By customizing themes, you can alter the default appearance of the Telerik components so they match the desired color scheme and the rest of your site's coloring and style.

This article contains the following sections:

When you use custom themes for Telerik UI for Blazor components, you must recreate the custom theme every time you update the Telerik components in your application. This ensures compatibility and allows you to get the theme updates and fixes.

Visual Customization Options

You can customize the appearance of the Telerik Blazor components in several ways. Each has pros and cons, and each is most suitable for specific scenarios and business requirements. The Blazor Theme Customization Options article offers a comparison between these CSS customization alternatives.

Using ThemeBuilder

ThemeBuilder is a web application that enables you to create new custom themes by changing the styles of existing built-in themes. Every change that you make is visualized almost instantly. Once you are done styling the UI components, you can export a ZIP file with the desired styles and use the custom theme in your Blazor app.

Setting Theme Variables

The Telerik themes define a collection of theme variables and values. Then, these variables take part in CSS rules to apply consistent styles to all Telerik Blazor components.

It is possible to customize the appearance of our components by overriding the theme variable values outside the theme CSS file. This spares the need to create and maintain a full custom theme.

Each theme defines the same collection of variables, but with different values:

The example below shows how to customize some of the theme variables.

Override theme variables

@if (RenderCustomVariables)
        :root {
            --kendo-color-base: #ddf;
            --kendo-color-base-hover: #eef;
            --kendo-color-base-active: #ccf;
            --kendo-color-on-base: #00c;

            --kendo-color-primary: #c00;
            --kendo-color-primary-hover: #c66;
            --kendo-color-primary-active: #900;
            --kendo-color-on-primary: #fee;

            --kendo-border-radius-md: 1rem;

            --kendo-font-size: 18px;

<p><label><TelerikCheckBox @bind-Value="@RenderCustomVariables" />
    Apply Custom Theme Variables</label></p>

<TelerikButton>Base Button</TelerikButton>

<TelerikButton ThemeColor="@ThemeConstants.Button.ThemeColor.Primary">
    Primary Button

@code {
    private bool RenderCustomVariables { get; set; } = true;

Building Themes From Source Code

The most complex and flexible way to use Telerik themes is to build them from the SASS source code in your development environment.

The Theme Customization page of the Progress Design System documentation and the kendo-themes repository wiki provide more information about this process.

Loading Custom Themes

Custom themes are used in a similar way as the built-in themes. The notable differences are:

  • The custom theme must reside in the wwwroot folder of the Blazor app or on a custom CDN provider.
  • You must recreate custom themes every time when you update the Telerik UI for Blazor version.

Make sure that the Blazor app is loading only one Telerik theme at a time. If you are replacing a built-in theme with a custom theme, you must remove the <link> element of the built-in theme.

You have your custom theme - either generated through the Telerik ThemeBuilder tool, or one that you built yourself, or something that your organization provides.

Adding a custom Telerik theme

    <!-- custom Telerik stylesheet in wwwroot/telerik/ -->
    <link rel="stylesheet" href="telerik/custom-theme.css" />

    <!-- other application stylesheets -->


To contribute to the development of the Kendo UI Themes, go to the telerik/kendo-themes GitHub repository.

See Also

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