Some users express their doubts on this wireless Wifi transfer. One of the most popular questions is that whether the original photos and videos will be deleted or not after they have been transferred to other devices successfully.
(Make sure the app is running on both devices.)
Of course, the answers is no. The iPhone WiFi Transfer cannot delete the original files. It just plays the role of an invisible USB cable. There is no need to worry about this problem. If you need to delete those files, you have to do that on the source devices. On the other hand, the files transferred to another device will not be deleted.
The reason is that Apple does not allow 3rd party apps to delete anything from the Photo library. So when transferring your photos & videos between iOS devices and computers, iPhone WiFi Transfer only copies files without removing them from the source devices.