Rendering Changes in 13.0.0

Updated on Feb 11, 2026

Apperance Classes

All applicable components render CSS classes for the following parameters only if these parameters are set explicitly:

• FillMode
• Rounded
• Size
• ThemeColor

For example, the following Telerik Button configuration...

RAZOR

<TelerikButton>Click Me</TelerikButton>

... produces the following HTML output:

UI for Blazor 12.3.0	UI for Blazor 13.0.0
HTML <button class="k-button k-button-solid k-rounded-md k-button-md k-button-solid-base"> <span class="k-button-text">Button Text</span> </button>	HTML <button class="k-button"> <span class="k-button-text">Button Text</span> </button>

To use the old rendering with more CSS classes in version 13.0.0, set the following parameters explicitly, for example:

• FillMode="@ThemeConstants.Button.FillMode.Solid" renders a class k-button-solid.
• Rounded="@ThemeConstants.Button.Rounded.Medium" renders a class k-rounded-md.
• Size="@ThemeConstants.Button.Size.Medium" renders a class k-button-md.
• ThemeColor="@ThemeConstants.Button.ThemeColor.Base" renders a class k-button-base. Note that this class differs in version 12.3.0 where it used to be k-button-solid-base.

Chat

• The AppBar component in the Chat header is replaced by a ToolBar component. The k-chat-header class is preserved.
• The TextArea component is replaced by a PromptBox component.
• The k-chat-file-wrapper CSS class is renamed to k-file-box-wrapper.
• The k-chat-file class is renamed to k-file-box.
• The k-chat-file-info class is renamed to k-file-info.
• The k-chat-file-size class is renamed to k-file-size.

TreeView

• The CaretAltRight and CaretAltDown expand/collapse icons are replaced by ChevronRight and ChevronDown.
• The k-treeview-top, k-treeview-mid, and k-treeview-bot classes are no longer used. The same <span> elements use a k-treeview-item-content class instead.
• The k-focus and k-selected classes are rendered on the parent span.k-treeview-item-content instead.

UI for Blazor 12.3.0	UI for Blazor 13.0.0
HTML <li class="k-treeview-item"> <span class="k-treeview-mid"> <span class="k-treeview-leaf k-focus k-selected"> <span class="k-treeview-leaf-text">Item Text</span> </span> </span> </li>	HTML <li class="k-treeview-item"> <span class="k-treeview-item-content k-focus k-selected"> <span class="k-treeview-leaf"> <span class="k-treeview-leaf-text">Item Text</span> </span> </span> </li>

See Also

• Use best practices when overriding theme styles
• Breaking changes in Telerik UI for Blazor 13.0.0