What is the difference between `remember` and `rememberSaveable` in Jetpack Compose?

Overview

remember

rememberSaveable

Comparison

remember

rememberSaveable

remember

kotlinCopy
@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }
    
    Button(onClick = { count++ }) {
        Text("Count: $count")
    }
}
// ❌ Lost on screen rotation

rememberSaveable

kotlinCopy
@Composable
fun Counter() {
    var count by rememberSaveable { mutableStateOf(0) }
    
    Button(onClick = { count++ }) {
        Text("Count: $count")
    }
}
// ✅ Survives screen rotation

What Are Configuration Changes?

• Screen rotation
• Language change
• Dark mode toggle
• Font size change
• Multi-window mode

Example: TextField

Without rememberSaveable

kotlinCopy
@Composable
fun LoginForm() {
    var email by remember { mutableStateOf("") }
    
    TextField(
        value = email,
        onValueChange = { email = it }
    )
}
// ❌ Text lost on rotation

With rememberSaveable

kotlinCopy
@Composable
fun LoginForm() {
    var email by rememberSaveable { mutableStateOf("") }
    
    TextField(
        value = email,
        onValueChange = { email = it }
    )
}
// ✅ Text preserved on rotation

Custom Objects

kotlinCopy
data class User(
    val name: String,
    val age: Int
) : Parcelable

@Composable
fun UserForm() {
    var user by rememberSaveable {
        mutableStateOf(User("Alice", 25))
    }
}

When to Use Which?

Use

textCopy

remember

• Temporary UI state
• Derived values
• Scroll positions (handled by framework)
• Animation states

Use

textCopy

rememberSaveable

• User input (TextField values)
• Selection state
• Expanded/collapsed states
• Form data

Performance Note

kotlinCopy
// Good
val expensiveComputation = remember {
    computeExpensive()
}

// Overkill
val expensiveComputation = rememberSaveable {
    computeExpensive()
}

Rule of Thumb: Use

textCopy

rememberSaveable

for user-facing state. Use

textCopy

remember

for everything else.