---
title: "Composable"
description: "[Composable] functions are the fundamental building blocks of an application built with Compose.

[Composable] can be applied to a function or lambda to indicate that the function/lambda can be
used as part of a composition to describe a transformation from application data into a tree or
hierarchy.

Annotating a function or expression with [Composable] changes the type of that function or
expression. For example, [Composable] functions can only ever be called from within another
[Composable] function. A useful mental model for [Composable] functions is that an implicit
\"composable context\" is passed into a [Composable] function, and is done so implicitly when it is
called from within another [Composable] function. This \"context\" can be used to store information
from previous executions of the function that happened at the same logical point of the tree."
type: "class"
---

<div class='type'>Class</div>


<a id='references'></a>

<div class='sourceset sourceset-common'>Common</div>


```kotlin
@MustBeDocumented
@Target(
    AnnotationTarget.FUNCTION,

    AnnotationTarget.TYPE,

    AnnotationTarget.TYPE_PARAMETER,

    AnnotationTarget.PROPERTY_GETTER,
)
public annotation class Composable
```


`Composable` functions are the fundamental building blocks of an application built with Compose.

`Composable` can be applied to a function or lambda to indicate that the function/lambda can be
used as part of a composition to describe a transformation from application data into a tree or
hierarchy.

Annotating a function or expression with `Composable` changes the type of that function or
expression. For example, `Composable` functions can only ever be called from within another
`Composable` function. A useful mental model for `Composable` functions is that an implicit
"composable context" is passed into a `Composable` function, and is done so implicitly when it is
called from within another `Composable` function. This "context" can be used to store information
from previous executions of the function that happened at the same logical point of the tree.