Two ways to put a phone on a TV
People often use the words mirroring and casting as if they were the same, but they work differently, and the difference explains most of the odd behaviour.
Screen mirroring copies what is on your phone’s screen to the television. Whatever you see on the phone, including menus and notifications, appears on the TV. The phone has to keep running and sending the picture the entire time.
Casting hands the job to the television or a connected device. When you press the cast button in a video app, your phone tells the TV which video to play. The TV then fetches the stream itself over your home network. The phone mostly acts as a remote control, so you can lock it, use other apps or even leave the room without stopping playback, though that depends on the app.
Both approaches usually travel over your home network, so they depend on the quality of your home Wi-Fi.
The main systems
Several technologies handle this, and which one you use depends on your devices.
- Google Cast is built into many televisions and streaming sticks. Compatible apps show a cast icon. It is mainly a casting system, though some phones can also mirror their screen through it.
- AirPlay is Apple’s system, found on Apple devices and many televisions and speakers made by other companies. It supports both casting video and mirroring a screen.
- Miracast is a mirroring standard that connects devices directly, without needing the home network in the middle. Support varies by phone and television, and some makers use their own name for it.
- Built-in smart TV features from television makers often provide their own mirroring and a companion app.
A phone and a TV must support a common system. Mixing ecosystems, such as an Apple phone with a television that lacks AirPlay, may need a streaming stick or box that supports your phone.
Wired options
A cable can be more dependable than wireless. Many phones can output video through an adapter that connects to an HDMI port on the TV. This avoids network problems and usually keeps delay low, which helps with games or presentations. The cost is a cable, an adapter that suits your phone’s port, and the loss of freedom to move about. Some phones and adapter types do not support video output, so check before buying.
Common problems and their causes
The phone cannot find the TV. The most common cause is that the two devices are on different networks. A home might have separate networks, or a guest network, or a router set to stop devices from talking to each other, sometimes called client isolation. Phone and TV need to be on the same network for most casting to work. Reviewing your home network and router settings often solves it. Powering off and on the TV or stick can also refresh its listing.
Video stutters or the picture is blocky. Wireless mirroring requires a steady stream of data. A weak signal, distance from the router or congestion from other devices can interrupt it. Moving closer, reducing other traffic or using a faster Wi-Fi band can help. The 5 GHz band typically carries more data than 2.4 GHz but has a shorter range, which is explained in the overview of Wi-Fi bands. If a TV is far from the router, a mesh Wi-Fi system or a wired Ethernet cable to the TV may help.
Sound and picture are out of step. Mirroring adds delay, and that is why it is poorly suited to fast games. Casting from an app usually keeps audio and video synchronised because the TV handles both. If the audio goes to a separate speaker or Bluetooth earbuds, that path can add more delay of its own.
The cast button is missing. The app may not support casting, or it may be that the phone cannot see a compatible device. Some apps limit casting for particular content.
Content is blocked or turns black. Protected content, such as some paid streaming programmes, may refuse to be mirrored. This is a rights-protection measure, a topic covered under digital rights management. Casting from within the official app typically works where mirroring does not.
Resolution looks low. Mirroring sends what the phone chooses to send, which may be a smaller picture than your TV can show. Casting lets the TV request the best version available. The question of what the television can display is discussed in the article on video resolution.
Photos and personal videos
For your own pictures and videos, both casting and mirroring work, and many gallery apps have a cast button. Casting a slideshow is generally smoother than mirroring a phone while you swipe. Sharing a family album this way is a pleasant use, especially if you keep your photo library organized into albums beforehand.
A short checklist
- Make sure the phone and TV are on the same network.
- Update the TV, stick and app if something misbehaves.
- Try casting from inside the app before trying mirroring.
- Move closer to the router, or consider a cable.
- Restart both devices, then try again.
Privacy while casting
While you mirror, whatever is on the screen can appear on the TV, including messages and notifications. Turning on a do-not-disturb mode before presenting avoids awkward moments. In shared spaces such as hotels or offices, check that you are connecting to your own device and not a similar-looking nearby one, and disconnect when you finish.