There is no easy way to transfer video file from your computer to your default video app, that's why I search the app store for the app that can do the wireless transfer for me, and I found the VLC, which is now the best app for me because not only is it free, but it will also basically play any kind of video file you throw at it.
How to transfer video/movies from your computer to your iPhone
Instruction
1. Make sure both your computer and the iOS device are on the same Wi-Fi network.
2. Then open the VLC app on your iOS device, and tap the vlc icon from the tap left corner.
3. From the sidebar menu, tap the “Sharing via WiFi” button to turn it on, It will now change to show an IP address and a “.local” address.
4. Go to your computer, and open your favorite browser (chrome, firefox, safart etc), then type the ip address or the local address from the vlc app.
5. This will take you to a page where you can either select the video/movies you want to transfer using the “+” at the right side of the screen or you can just drop in the files to the page. You can transfer video files vice versa.
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