The future perfect simple tense in English grammar indicates that an action will have been completed by a certain future time.
We can use the English future perfect tense for:
actions that will have been finished by a future time, usually with an expression of time
Example: Don’t worry, he will have repaired the bike by then.
assumptions about something that has probably happened
Example: He will probably have noticed that his bike is broken.
Some examples of signal words or expressions for the future perfect are: by Monday, in a week etc.
To conjugate the future perfect tense, we follow the rule: will + have + past participle.