Version: 2021.3
UI Builder
Get started with UI Builder

Interface overview

This is the main UI Builder Editor Window:

UI Builder Main Window
UI Builder Main Window


StyleSheets and the USS Selectors within in UI Toolkit are used to share and apply styles across many elements and many UI Documents (UXML).

The StyleSheets pane 1 is where you can:

  1. Add, reorder, or remove StyleSheets (USS) to the current UI Document (UXML).
  2. Create, reorder, copy, or remove USS Selectors within StyleSheets for sharing styles across many elements.


The Hierarchy pane 2 contains the tree view representing the element hierarchy of the current document. It’s a superset of the hierarchy you see in the UXML text representation of the UI Document (UXML). Besides the elements created directly from UXML, the Hierarchy pane also contains elements created dynamically and only exist in the runtime of the UI. For example, the Hierarchy pane includes elements that are part of a Template instance (a different document instanced inside the current document), where the UXML would just has a single <Instance> tag.

You can use the Hierarchy pane to:

  1. Select elements for inspecting or editing.
  2. Cut, copy, delete, or reorder elements.
  3. Open instanced template documents as sub-documents for in-place (in context) editing.
  4. See at once many elements’ style class lists, name attributes, and locally attached StyleSheets.

Elements appear in the tree according to their name attributes. If an element’s name attribute is not set, it appears according to its C# type. You can double-click an element to quickly rename it.

Click the icon in the top right corner of the Hierarchy pane header to access a menu of display options.

  • Select Type to force the Hierarchy to display each element’s C# type, regardless of whether it has a name.
  • Select Class List to display each element’s style class list next to its Hierarchy entry.
  • Select Attached StyleSheets to display any locally attached StyleSheets next to their element.


The Library pane 3 is similar to the Project window in the Unity Editor. It lists available UI elements.

  • The Standard tab lists the standard built-in elements that Unity provides. These elements include standard styling that works for all supported Unity Editor and runtime themes.

You can change this view mode between tiles and tree view using the icon in the top right corner of the Library window and choosing Tree View.

  • The Project tab lists custom .uxml assets in the Project. It also lists any custom C# elements that inherit from VisualElement and have their UxmlFactory set up to be instantiable via UXML. To preview any element in the Library’s Project tab, hover over it. The preview appears to the right of the Library pane.

To instantiate an element, do one of the following:

  • Drag it into the Hierarchy pane.
  • Drag it onto the Canvas in the Viewport.
  • Double-click it. This adds the element as a sibling of the currently selected element. If nothing is selected, the element is added at the root of the UI Document (UXML).


The Viewport pane 4 displays the output of a UI Document (UXML) on a floating resizable edit-time Canvas.

  • The header of the Canvas displays the name of the currently loaded UI Document (UXML). An asterisk (*) next to the name indicates unsaved changes.
  • The toolbar contains menus of UI Builder-specific commands, Viewport settings, Theme selector, and the Preview button.
  • You can find additional UI Builder settings in the top-right corner of the Viewport under the menu, including a shortcut to the UI Builder’s Settings in Unity’s Project Settings.
  • The Canvas is where you edit, preview, and interact with the UI Document (UXML) you are authoring.
  • You can change Canvas settings by clicking on the Canvas header and accessing the Inspector.

Navigating in the viewport

Pan and zoom to navigate in the viewport. The UI Builder saves each UI Document (UXML)’s current pan and zoom state, and restores them after the UI Builder window reloads, a domain reload, or when you close and re-open the same UI Document (UXML).

When you create and open a new document, the UI Builder resets the pan and zoom states.

To pan, do one of the following:

  1. Middle-click and drag in the Viewport.
  2. Hold down Ctrl/Cmd + Alt/Option and click and drag in the Viewport.

To zoom in and out, position the mouse pointer in the Viewport and do one of the following:

  1. Position the mouse pointer in the viewport, and rotate the mouse wheel.
  2. Hold down Alt/Option and right-mouse drag. Drag right to zoom in, and left to zoom out.

Code Previews

As you build your UI, UI Builder automatically generates the underlying UXML and USS text, and displays them in the UXML Preview and USS Preview panes 5.


The UI Builder Inspector pane 6 is similar to the Unity Inspector window. The Inspector will display slightly different content, depending on the object you have selected inside the UI Builder:

  1. Elements display an Attribute section for per-element (UXML) attributes, a StyleSheets section for assigning style classes and viewing applied styles from StyleSheets, and an Inlined Styles section that allows editing of inline per-element style properties.
  2. USS Selectors display a Style Selector section for changing the selector query string and a Styles section for editing of style properties.
  3. Canvas displays a Canvas Size section for changing the Canvas size, a Canvas Background section for changing the edit-time canvas background, and a Document Settings section for per-document edit-time settings.
UI Builder
Get started with UI Builder
Copyright © 2023 Unity Technologies
优美缔软件(上海)有限公司 版权所有
"Unity"、Unity 徽标及其他 Unity 商标是 Unity Technologies 或其附属机构在美国及其他地区的商标或注册商标。其他名称或品牌是其各自所有者的商标。