A REPLAY file contains a replay of gameplay in Fortnite, a sandbox survival where players cooperate to collect resources, build fortifications, and fight enemy creatures. It stores game information used by Fortnite to replay gameplay. REPLAY files allow Fortnite users to save their replays and rewatch them for entertainment or strategic purposes.

REPLAY files can only be played by Fortnite. Also, the files do not store actual video and cannot be converted to a video file. If you want to share a REPLAY file and play it in a different program, you must use a screen recording program to record the playback of the REPLAY file. To do this, start a recording of your screen, play the REPLAY file in Fortnite, then end and save the recording. You can then share the newly-saved video file with another user.