Animations

Avalonia provides three types of animations:

Type	Description	Use case
Keyframe Animations	Change one or more properties over a timeline with multiple keyframes.	Complex, multi-step animations triggered by style selectors.
Control Transitions	Animate a single property when its value changes.	Smooth visual feedback for property changes (opacity, color, size).
Composition Animations	Code-driven animations that run on the render thread.	Performance-sensitive or programmatic animations controlled from C#.

Additionally, Page Transitions animate content switching in controls like TransitioningContentControl and Carousel.

Keyframe animations

The simplest keyframe animation changes one property value over a specified duration by defining two keyframes: one at the start (0%) and one at the end (100%).

The property value is interpolated between keyframes using an easing function. The default is linear interpolation.

Quick example

<Border Background="Blue" Width="100" Height="100">
    <Border.Styles>
        <Style Selector="Border">
            <Style.Animations>
                <Animation Duration="0:0:1" IterationCount="INFINITE"
                           PlaybackDirection="Alternate">
                    <KeyFrame Cue="0%">
                        <Setter Property="Opacity" Value="1.0" />
                    </KeyFrame>
                    <KeyFrame Cue="100%">
                        <Setter Property="Opacity" Value="0.3" />
                    </KeyFrame>
                </Animation>
            </Style.Animations>
        </Style>
    </Border.Styles>
</Border>

This creates a pulsing opacity animation that runs forever, alternating between full and partial opacity.

See Keyframe Animations for the full syntax and more examples.

Control transitions

Transitions animate a property whenever its value changes, providing smooth visual feedback without writing explicit keyframes:

<Button Content="Hover me" Background="Blue">
    <Button.Transitions>
        <Transitions>
            <BrushTransition Property="Background" Duration="0:0:0.3" />
            <DoubleTransition Property="Opacity" Duration="0:0:0.2" />
        </Transitions>
    </Button.Transitions>
</Button>

See Control Transitions for transition types and configuration.

Composition animations

Composition animations provide a lower-level, code-driven approach that runs on the render thread. Use them when you need programmatic control or render-thread performance:

var visual = ElementComposition.GetElementVisual(myControl);
var compositor = visual.Compositor;

var animation = compositor.CreateVector3KeyFrameAnimation();
animation.Duration = TimeSpan.FromMilliseconds(400);
animation.InsertKeyFrame(0f, new Vector3D(-200, 0, 0));
animation.InsertKeyFrame(1f, new Vector3D(0, 0, 0));

visual.StartAnimation("Offset", animation);

See Composition Animations for the full API, implicit animations, and integration patterns.

Triggering animations

Keyframe animations defined in XAML rely on style selectors for their triggering behavior:

• Unconditional selector (e.g., Style Selector="Border"): The animation starts when the control enters the visual tree.
• Conditional selector (e.g., Style Selector="Border:pointerover"): The animation runs when the selector condition matches (e.g., pointer is over the border) and stops when it no longer matches.

XAML

<UserControl xmlns="https://github.com/avaloniaui">
  <UserControl.Styles>
    <Style Selector="Border:pointerover">
      <Style.Animations>
        <Animation Duration="0:0:2">
            <KeyFrame Cue="100%">
                <Setter Property="ScaleTransform.ScaleX" Value="1.5" />
                <Setter Property="ScaleTransform.ScaleY" Value="1.5" />
            </KeyFrame>
        </Animation>
      </Style.Animations>
    </Style>
  </UserControl.Styles>

  <Border Width="100" Height="100" Background="blue" />
</UserControl>

Preview

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info

By default, a style-applied keyframe animation pauses when its control is effectively invisible, and resumes when the control is visible again. See Playback behavior.

Animation settings

Keyframe animations support these configuration options:

Setting	Description	Example
Duration	How long one cycle takes.	0:0:1 (1 second)
Delay	Time to wait before starting.	0:0:0.5
Easing	The interpolation curve between keyframes.	CubicEaseInOut
FillMode	What happens when the animation ends.	Forward, Backward, Both, None
IterationCount	Number of times to repeat. Use infinite for forever.	3, INFINITE
PlaybackBehavior	Whether to pause the animation when the control is hidden.	Normal, Reverse, Alternate, AlternateReverse
PlaybackDirection	Direction of playback.	Auto, Always, OnlyIfVisible

See Animation Settings for details on each option and Easing Functions for all available easing types.

See also

• Keyframe Animations: Full keyframe animation syntax and examples.
• Control Transitions: Animating property changes.
• Composition Animations: Code-driven render-thread animations.
• Page Transitions: Animating content switching.