[android-components](../../../index.md) / [mozilla.components.concept.engine](../../index.md) / [EngineSession](../index.md) / [Observer](index.md) / [onThumbnailChange](./on-thumbnail-change.md)

# onThumbnailChange

`open fun onThumbnailChange(bitmap: `[`Bitmap`](https://developer.android.com/reference/android/graphics/Bitmap.html)`?): `[`Unit`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-unit/index.html) [(source)](https://github.com/mozilla-mobile/android-components/blob/master/components/concept/engine/src/main/java/mozilla/components/concept/engine/EngineSession.kt#L43)