U-Selector syntax

U-Selector finds GameObjects the way CSS selectors find HTML elements. query_objects, wait_for_selector, assert_ui_state, simulate_input (ui_click), batch_modify and the steps of run_e2e_test all take one.

#Player                 by name
#Enemy*                 name with wildcards (* any text, ? one character)
.Camera                 by component type
/Canvas/Menu/PlayButton by hierarchy path
[tag=Player]            by attribute
.Enemy[tag=Boss]        component type and attribute
ui:#StartButton         UI Toolkit element by name
ui:.menu-item           UI Toolkit elements by USS class
ui:Button               UI Toolkit elements by type

Name — #Name

Matches the GameObject name exactly. * and ? make it a pattern: #Enemy* (starts with), #*Spawner (ends with), #*Boss* (contains). A selector without a prefix is also treated as a name.

Component — .Type

Matches GameObjects that have a component of that type, such as .Camera, .Rigidbody or your own .EnemyController.

Path — /Parent/Child

Matches by hierarchy path from a root object.

Attribute — [name op value]

Operators: =, !=, >, <. Attribute names:

Attribute	Value
name	GameObject name
tag	Tag
layer	Layer number
active	Active in the hierarchy
activeSelf	Own active flag
anything else	A public property of one of the object’s components, e.g. [enabled=false]

Combine with a type to narrow the search: .Enemy[tag=Boss].

UI Toolkit — ui:

A ui: prefix searches the visual trees of all UIDocuments in the scene: ui:#name, ui:.uss-class or a type name such as ui:Button.