Screen mirroring that doesn't go through anyone's servers
Does screen mirroring send my screen over the internet?
It depends entirely on the app, and the difference is large. Some route your screen through a server. Others keep it on your own network. Screen mirroring sees everything on your display (messages, banking, photos), so it is worth knowing which kind you have installed.
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Screen mirroring is an unusually invasive permission. An app with it sees your notifications, your messages as they arrive, your banking app, your photos, whatever is on the display. That is not a reason to avoid it, but it is a reason to know where the data goes.
The three architectures
Local only. The phone sends directly to the television across your own Wi-Fi. No server is involved because there is none. If your internet connection dropped, mirroring would continue. This is how Vistacast works, and it is why there is no account to create.
Server-relayed. The phone uploads to a server and the television downloads from it. This is how apps that work across different networks manage it, and it is a genuine feature, but your screen leaves your house. Whether it is stored, for how long, and who can see it depends entirely on that company’s policy.
Local, with a cloud dependency. Traffic stays local, but the app checks in with a server for licensing, analytics or crash reporting. Your screen is not uploaded; your usage is.
None of these is dishonest by itself. What matters is knowing which you have.
How to tell which one you have
You do not have to take a marketing page’s word for it, including this one.
Does it need an account? An account implies a server, and a server implies your usage is recorded. Local-only mirroring has nothing to authenticate against.
Does it work with the internet off? The clearest test there is. Disconnect your router from the internet while leaving Wi-Fi running. Local mirroring keeps working. Anything that stops was relying on something outside your house.
Read the App Store privacy card. Apple requires developers to declare what they collect. “Data Not Collected” is a meaningful claim: Apple can act against a false declaration.
Check what the privacy policy is scoped to. A policy that says “we collect no data” while the company’s website runs three analytics services is technically accurate about the app and quietly incomplete. Ours addresses both the apps and this website separately, because they genuinely are different.
Where we are less than perfect
Being specific about this is more useful than a reassuring summary.
Vistacast attempts an encrypted connection to the television, and some television chipsets cannot complete the handshake. On those, it falls back to an unencrypted connection within your local network so mirroring still works. The app also does not yet verify the receiver’s identity, which means that on a network you do not control (shared, public or workplace Wi-Fi), another device on that network could in principle present itself as a receiver.
On your own home network neither of these is a practical concern. On a network you do not control, both are worth weighing. Receiver authentication is a known gap rather than a design choice, and we would rather write that down than describe the connection as simply “encrypted”.
What local-only costs you
Honesty cuts both ways. Keeping everything local means:
- Both devices must be on the same network. No mirroring to a television in another building.
- Networks that isolate their clients will not work at all, and no server-side workaround is available.
- Nobody can look at logs to diagnose your problem, because there are none. Support is you describing the symptom.
That is the trade. For a lot of people, a product that cannot leak what it never receives is worth those limits.