Play videos and slideshows in the Photos app on iPhone
Use the Photos app to play videos you’ve recorded or saved on your iPhone. You can also create slideshows of the photos, videos, and Live Photos in your library.
Play a video
As you browse photos and videos in the Photos app, tap a video to play it on your iPhone. While it plays, you can do any of the following:
Tap the player controls below the video to pause, unmute, favorite, share, delete, or see video information; tap the screen to hide the player controls.
Double-tap the screen to switch between full screen and fit-to-screen.
Touch and hold the frame viewer at the bottom of the screen to pause the video, then slide the viewer left or right to move back or forward.

Make and play a slideshow
You can create a slideshow to view a collection of photos and videos that you choose from your library. Slideshows are automatically formatted and set to music.
Tap Library, then view photos by All Photos or Days.
Tap Select.
Tap each photo you want to include in the slideshow, then tap
.
Tap Slideshow from the list of options.
To change the slideshow theme, music, and more, tap the screen while the slideshow plays, then tap Options.
Note: You can also make a slideshow from an album. Tap Albums, tap the album you want to create a slideshow from, then follow the steps above.