In OS X 10.10 Yosemite, Apple added a new and extremely useful feature that allows us to easily capture the screen of an iOS device on the Mac itself. The feature was implemented to help developers with app previews, which Apple introduced as part of iOS 8‘s improvements to the App Store, but it’s definitely not limited to devs only.
FSM EXCLUSIVE DEAL Pluggin into a Mac that’s running OS X 10.10, via USB, an iPhone or iPad running iOS 8, the iOS device will now show up as a standard camera input which means that any video app can be used to record the screen of the iOS device without the need for additional hardware or software.
If you’re jailbroken you can use DisplayRecorder to record the screen of your iOS device, and other tweaks which are specifically dedicated to recording a live iOS device screencast via AirPlay Mirroring. Also, now you can use an Apple HDMI cable in combination with a dedicated capture device to record your iOS screen.
But, the new feature dramatically simplifies the process. With iOS 8 beta 1 and OS X 10.10 Yosamite DP1, the recording appears to be extremely laggy. However, as more beta updates will be released, video quality will definitely improve significantly as both OS’ will approach a public release.