What app uses blurry photo as background photo with a picture on top of it?

I keep seeing photos on instagram where they have a picture on top of another picure but the picture behind the other photo (the background photo) is a blurry photo. What app are they using to create this blurred effect with a photo overlapped on top of the blurred photo? This means both photos are the same but one is on top while the background photo has a blurred effect or frosted glass effect added to it.

The app "BlurBackground" does this as shown in the screenshot below. This app includes a variety of background blur effects including the picture in a picture frosted glass effect as shown. You can adjust the blur clarity on every effect to make it lighter or thicker.