The future perfect progressive tense is used for an ongoing action that will be completed at some specified time in the future. For example: John will have been baking a cake. They will have been painting the fence.

Why do we use future perfect progressive tense?

The future perfect progressive tense, also known as the future perfect continuous tense, is used to indicate a continuous action in the future.

How do we differentiate future perfect from future perfect progressive?

The future perfect describes an action that will end in the future. The future continuous describes an action that will continue in the future. If you're still having trouble picturing this difference, below is a comic strip that can help you easily understand and master these two ways of talking about future actions.