“Loop a video” can mean three different things on an iPhone: apply a Loop effect to a Live Photo, repeatedly play an ordinary video, or create a new video file that contains repeated copies of the clip. Choose the method that matches what you want to do.
Loop a Live Photo in Photos
Open Photos and select a Live Photo. Use the Live Photo effects control and choose Loop. Photos turns the captured Live Photo motion into a repeating effect. Bounce is another Live Photo effect that plays the motion forward and backward.
These Loop and Bounce controls are for Live Photos. Do not expect the same controls when you open an ordinary video file.
Replay an ordinary video
If you only want a normal video to repeat while you watch it, use a video player or app that provides repeat playback. This changes how the clip plays on that device; it does not necessarily create a new file containing repeated footage.
If the repetition needs to remain after you send, post, or upload the video, use a video editor. Import the clip, duplicate it on the timeline, place the copies back to back, and export the project as a new video. The repetition is then part of the exported file.
Avoid slideshow workarounds for ordinary video looping
Slideshows and presentation features can change between iOS versions and are not the clearest way to create a true looped video. They can also add transitions or music that you did not want. Use Live Photo effects for Live Photos, repeat playback for viewing, and timeline duplication for a self-contained repeated video.
Keep the original clip
Save the original before exporting an edited loop. Repeating a clip several times increases the duration and usually the file size, so choose the number of repetitions based on where you plan to share it.
Matthew Roberts created this site to help his friends and family with questions that they might have about how to change the settings on their iPhones. It now serves as an archive of iPhone how-to guides to help anyone that stumbles upon this website.