Annotations

@ComposePreview is the entry point for generated previews. It declares the preview name, owning group, optional description, tags, and optional variant family metadata.

Groups and tags

Groups and tags are regular Kotlin hierarchies:

sealed interface MyGroup : PreviewGroup {
    data object Components : MyGroup {
        override val name = "Components"
    }
}

sealed interface MyTag : PreviewTag {
    data object Button : MyTag {
        override val title = "button"
    }
}

Identity comes from the type itself. name and title are only labels shown in the UI.

Annotating a preview

@ComposePreview(
    name = "Primary Button",
    group = MyGroup.Components::class,
    description = "Default button style",
    tags = [MyTag.Button::class],
)
@Composable
fun PrimaryButtonPreview() {
    PrimaryButton(label = "Click me")
}

What @PreviewParam is for

@PreviewParam is intentionally basic mode. It works well for common scalar parameters where the annotation alone should describe the control.

@Composable
fun InboxSummaryPreview(
    @PreviewParam(label = "Filter") filter: InboxFilter = InboxFilter.All,
    @PreviewParam(label = "Notifications") notificationsEnabled: Boolean = true,
) {
    ...
}

Rules:

• The annotated parameter must have a Kotlin default value in the function signature.
• The function default is the single source of truth.
• options is available when you want a constrained string-backed picker.

When one preview needs a more expressive control surface, keep discovery via annotations and attach a richer parameter form through a preview override instead of abandoning generated previews entirely.