Twitter started rolling out autoplay videos to its iOS app on June, 16, 2015. This means all animated GIFs, Vines, and videos will automatically play when you scroll through your Twitter feed. This isn't only annoying, but it can also eat up your data plan when you're not using a Wi-Fi connection. Here's how to disable autoplay videos when using the iOS app:
1. Open the Twitter app on your device.
2. Tap the "Me" icon in the lower-right hand corner of the app.
3. Tap the Gear icon next above your Twitter handle.
4. Select Settings from the pop-up box.
5. Under General tap “Video autoplay” and choose “Use mobile data and Wi-Fi”, “Use Wi-Fi only” or “Never play videos automatically.”