Since the wallpaper editor turns GIFs into still images, you need to convert the GIF you want to use as your lock screen wallpaper to a Live Photo, a format that will animate whenever you press on the screen. Don't Miss: Get Apple's Very First iPhone Wallpaper on Your Home or Lock Screen.Still, there's a whole world of GIFs out there, so why limit yourself to one or two live wallpapers from Apple?
The live options vary depending on your iPhone model and software version, but there should always be a few to choose from. If you want an animated wallpaper on your lock screen in iOS 15.6 or older, the easiest thing to do is go to Settings –> Wallpaper –> Choose a New Wallpaper, then select one of Apple's available 'Live' wallpapers. It's an annoying limitation on iOS, but one that's easily bypassed with a tiny bit of work. You can set a GIF as the wallpaper for your iPhone's lock screen, but it won't animate like it does when looking at the image in the Photos app.