---
title: "BlurRadiusSpec"
description: "Configures varying blur radius across a surface."
type: "interface"
lastmod: "2026-09-24"
---
## API Reference

> Source set: Common

```kotlin
public sealed interface BlurRadiusSpec
```

Configures varying blur radius across a surface.

Obtain instances from companion factories and pass them to `androidx.compose.ui.draw.blur`, or
realize them into a [RenderEffect](/jetpack-compose/androidx.compose.ui/ui-graphics/classes/RenderEffect/api) with `createRenderEffect`.

Uniform radii (`uniform`) are supported on Android 12 (API 31)+. Spatially-varying radii require
Android 13 (API 33)+. Unsupported configurations render the content unblurred.

Every length in the configuration, including gradient geometry, is expressed in `Dp` and resolves
against the layer's size and density at draw time. The `shader` shader is the exception: it
evaluates in layer pixel coordinates and returns a unitless 0..1 intensity. Spatially-varying
radii cap at 150px once resolved; `uniform` radii are not capped.

## Functions

### createRenderEffect

> Source set: Common

```kotlin
public fun createRenderEffect(
        size: Size,
        density: Density,
        edgeTreatment: TileMode = TileMode.Clamp,
    ): RenderEffect
```

Creates a [RenderEffect](/jetpack-compose/androidx.compose.ui/ui-graphics/classes/RenderEffect/api) that applies this blur configuration.

Assign the result to a graphics layer for low-level control, or prefer the block-based
`androidx.compose.ui.draw.blur` overload, which manages the effect automatically.

The effect resolves this configuration against `size` and `density` at creation, so create a
new effect whenever the configuration or the layer size changes — for example inside a
`androidx.compose.ui.graphics.graphicsLayer` block where the layer size is known.

Platform support varies with the configuration; query availability at runtime with
`RenderEffect.isSupported`. Unsupported platforms and zero radii render content unblurred.

#### Parameters

| | |
| --- | --- |
| size | size of the layer being blurred, in pixels |
| density | density used to resolve [Dp](/jetpack-compose/androidx.compose.ui/ui-unit/classes/Dp) radii to pixels |
| edgeTreatment | strategy used to sample pixels outside the content bounds |

#### Return

[RenderEffect](/jetpack-compose/androidx.compose.ui/ui-graphics/classes/RenderEffect) applying the progressive blur

## Members

### Companion

> Source set: Common

```kotlin
public companion object
```

## Functions

### uniform

> Source set: Common

```kotlin
public fun uniform(radius: Dp): BlurRadiusSpec
```

Creates a uniform blur `radius` across the surface.

Supported on Android 12 (API 31) and above. Older platforms and unsupported
configurations render the content unblurred.

#### Parameters

| | |
| --- | --- |
| radius | blur radius across the surface |

#### Throws: IllegalArgumentException

if `radius` is negative

### verticalGradient

> Source set: Common

```kotlin
public fun verticalGradient(startRadius: Dp, endRadius: Dp): BlurRadiusSpec
```

Creates a vertical blur gradient from `startRadius` at top to `endRadius` at bottom.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

#### Parameters

| | |
| --- | --- |
| startRadius | blur radius at the top |
| endRadius | blur radius at the bottom |

#### Throws: IllegalArgumentException

if either radius is negative

### verticalGradient

> Source set: Common

```kotlin
public fun verticalGradient(stops: List<BlurStop>): BlurRadiusSpec
```

Creates a vertical multi-stop blur gradient from top to bottom.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

Accepts `stops` in any order and sorts them stably by `BlurStop.fraction`.

#### Parameters

| | |
| --- | --- |
| stops | list of blur stops defining the gradient |

#### Throws: IllegalArgumentException

if the stop count is outside 2..16

### horizontalGradient

> Source set: Common

```kotlin
public fun horizontalGradient(startRadius: Dp, endRadius: Dp): BlurRadiusSpec
```

Creates a horizontal blur gradient from `startRadius` at left to `endRadius` at right.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

#### Parameters

| | |
| --- | --- |
| startRadius | blur radius at the left |
| endRadius | blur radius at the right |

#### Throws: IllegalArgumentException

if either radius is negative

### horizontalGradient

> Source set: Common

```kotlin
public fun horizontalGradient(stops: List<BlurStop>): BlurRadiusSpec
```

Creates a horizontal multi-stop blur gradient from left to right.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

Accepts `stops` in any order and sorts them stably by `BlurStop.fraction`.

#### Parameters

| | |
| --- | --- |
| stops | list of blur stops defining the gradient |

#### Throws: IllegalArgumentException

if the stop count is outside 2..16

### linearGradient

> Source set: Common

```kotlin
public fun linearGradient(
            start: DpOffset,
            end: DpOffset,
            startRadius: Dp,
            endRadius: Dp,
        ): BlurRadiusSpec
```

Creates a linear blur gradient from `startRadius` at `start` to `endRadius` at `end`.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

#### Parameters

| | |
| --- | --- |
| start | start position within the layer |
| end | end position within the layer |
| startRadius | blur radius at `start` |
| endRadius | blur radius at `end` |

#### Throws: IllegalArgumentException

if either radius is negative

### linearGradient

> Source set: Common

```kotlin
public fun linearGradient(
            start: DpOffset,
            end: DpOffset,
            stops: List<BlurStop>,
        ): BlurRadiusSpec
```

Creates a linear multi-stop blur gradient along the `start` to `end` line.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

Accepts `stops` in any order and sorts them stably by `BlurStop.fraction`.

#### Parameters

| | |
| --- | --- |
| start | start position within the layer |
| end | end position within the layer |
| stops | list of blur stops defining the gradient |

#### Throws: IllegalArgumentException

if the stop count is outside 2..16

### radialGradient

> Source set: Common

```kotlin
public fun radialGradient(
            startRadius: Dp,
            endRadius: Dp,
            center: DpOffset = DpOffset.Unspecified,
            fallOffRadius: Dp = Dp.Infinity,
        ): BlurRadiusSpec
```

Creates a radial blur gradient from `startRadius` at `center` to `endRadius` at
`fallOffRadius`.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

#### Parameters

| | |
| --- | --- |
| startRadius | blur radius at the center of the gradient |
| endRadius | blur radius at the falloff distance |
| center | center of the gradient within the layer, or `DpOffset.Unspecified` for the surface center |
| fallOffRadius | distance from [center](/jetpack-compose/androidx.compose.ui/ui-geometry/properties/center) at which `endRadius` is reached; defaults to half the surface's minimum dimension |

#### Throws: IllegalArgumentException

if either radius is negative, or `fallOffRadius` is finite and not positive

### radialGradient

> Source set: Common

```kotlin
public fun radialGradient(
            stops: List<BlurStop>,
            center: DpOffset = DpOffset.Unspecified,
            fallOffRadius: Dp = Dp.Infinity,
        ): BlurRadiusSpec
```

Creates a radial multi-stop blur gradient from `center` to `fallOffRadius`.

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

Accepts `stops` in any order and sorts them stably by `BlurStop.fraction`.

#### Parameters

| | |
| --- | --- |
| stops | list of blur stops defining the gradient |
| center | center of the gradient within the layer, or `DpOffset.Unspecified` for the surface center |
| fallOffRadius | distance from [center](/jetpack-compose/androidx.compose.ui/ui-geometry/properties/center) at which fraction 1 is reached; defaults to half the surface's minimum dimension |

#### Throws: IllegalArgumentException

if the stop count is outside 2..16

#### Throws: IllegalArgumentException

if `fallOffRadius` is finite and not positive

### shader

> Source set: Common

```kotlin
public fun shader(maxRadius: Dp, block: Density.(sizePx: Size) -> Shader): BlurRadiusSpec
```

Creates a custom blur intensity mask driven by a [Shader](/jetpack-compose/androidx.compose.ui/ui-graphics/classes/Shader/api).

Supported on Android 13 (API 33) and above. Older platforms and unsupported
configurations render the content unblurred.

Invokes `block` once per draw with the layer's `Size` and `Density`. Mutate the returned
shader's uniforms between frames to animate the blur. The shader evaluates in layer pixel
coordinates from the top-left origin. Its sampled alpha channel is a 0..1 intensity
scaling `maxRadius`; values outside that range are clamped. Any [Shader](/jetpack-compose/androidx.compose.ui/ui-graphics/classes/Shader/api) can serve as the
mask, including gradients from `androidx.compose.ui.graphics.ShaderBrush`.

The `Size` passed to `block` is in pixels.

Create the shader once and reuse it across frames. Each call returns a new configuration
that never compares equal, defeating downstream caching.

#### Parameters

| | |
| --- | --- |
| maxRadius | maximum blur radius scaled by the shader alpha |
| block | builder producing a [Shader](/jetpack-compose/androidx.compose.ui/ui-graphics/classes/Shader) given the layer size and density |

#### Throws: IllegalArgumentException

if `maxRadius` is negative