First you have to be clear about wether you want to connect your iPad or iPhone using a cable or Airplay.
You need your USB-C or Lightning to HDMI/VGA/Display-Port/USB-C adapter or cable and connect it to your monitor.
<aside> ⚠️ iOS 15 issue: On some iOS 15 devices it can take up to two minutes for them to recognise a cable-monitor connection. This is an iOS and not a shiftscreen problem.
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For Airplay, you have to use your control center. Follow the Apple guide for opening the control center (iPad or iPhone).
Now select the Airplay device to which you want to connect to.
The device you want to connect you needs to be Airplay capable and you need to be on the same network.
<aside> ☝ Common issue: instead of connecting you screen to Airplay, you only connect the audio output. Pressing on the audio Airplay symbol is wrong, make sure to use the video.
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<aside> 💡 Since MacOS Monterey your MacBook can also now be used as a second screen using Airplay.
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Now let’s take a look at different monitor problems, you might encounter. In general you have to understand that the reasons for monitor issues are iOS itself, the used cable connector or the monitor.
Having black bars on the side or on top is called underscan and this is intended behavior caused by iOS. In shiftscreen you can circumvent this by choosing a different overscan mode in the current monitor configuration. Like for example the scale mode.
Then the picture will most likely be too big, so take a look at how to deal with overscan.
Overscan is an issue caused by your monitor and iOS. Since the picture is too big we need to reduce the monitor size. You can do so by setting the horizontal space or vertical space in the current monitor configuration.
A stretched picture often happens with older/slower devices and is caused by iOS, the used cable and the monitor. Often times, buying and using different cables (with differente connection technologies like HDMI or Display-Port) can resolve this issue. If this does not help, you can use a shiftscreen monitor configuration profile.
