mutableStateOf vs derivedStateOf — Jetpack Compose

A small Compose concept that can make a big difference when managing state and recomposition.

mutableStateOf → stores state

Use it when your value is the source of truth and can be changed directly.

var count by remember { mutableStateOf(0) }

Here, count is the actual UI state. When it changes, Compose can recompose the parts of the UI that read it.

derivedStateOf → derives state

Use it when you need to calculate a value from existing state.

var count by remember { mutableStateOf(0) }

val isEven by remember {
    derivedStateOf { count % 2 == 0 }
}

Now:

  • count → source state

  • isEven → derived state

  • isEven doesn't need to be stored separately

  • Compose tracks the states read inside the derived calculation

Simple rule 🧠

Storing a value? → mutableStateOf
Calculating a value from state? → derivedStateOf

One important point: derivedStateOf isn't something you should add to every calculated expression. It is most useful when the derived value changes less frequently than the inputs and you want to avoid unnecessary recompositions.

Understanding this distinction helps you write cleaner and more efficient Jetpack Compose code.

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