How QR codes work for mobile app testing
The QR code displayed in VS-REP connects your phone's Expo Go app to your development server. When scanned, it tells Expo Go where to download and run your app's JavaScript code.
The QR code is a link to your live development server, not a snapshot of your app. This means anyone who scans it always gets the latest version of your code.
User opens Expo Go and scans
Phone connects to VS-REP URL
Latest JavaScript is fetched
App launches on device
The QR code URL is tied to your VS-REP project and development server session. Here's when it changes and when it stays the same:
npm run dev again can generate a new session
There is no preset expiration timer on QR codes. The URL only becomes invalid if the development server stops running.
Yes! As long as your VS-REP project is running, old QR codes continue to work. VS-REP provides stable URLs, so the QR code you shared last week should still function today.
| Scenario | Does Old QR Work? | What Happens |
|---|---|---|
| VS-REP is running | Yes | User sees your latest app version |
| VS-REP is sleeping/stopped | No | Connection fails - user sees error |
| You restarted VS-REP | Usually Yes | Same URL, should reconnect |
| You made code changes | Yes | User gets the new changes automatically |
The QR code doesn't point to a specific "build" or version. It points to your live development server. Every time someone opens the app or refreshes, they pull the newest JavaScript bundle automatically.
Yes! The QR code is safe to share publicly. However, keep in mind that your VS-REP must be running for others to access the app. Consider keeping your project always-on if you're sharing with many testers.
Most likely your VS-REP is not running. Check if the development server is active. If it's sleeping, start it up and the same QR code should work again.
No! This is the beauty of Expo Go development. The QR code is a permanent link to your live server. All updates are delivered automatically - no new QR codes required.
Changing the VS-REP project name may change the URL, which would require a new QR code. However, simple code changes, even major feature updates, do not affect the QR code.
There's no hard limit, but performance may degrade with many simultaneous connections to a development server. For large-scale testing, consider using EAS Build to create standalone test builds.
Absolutely! Printed QR codes work the same as digital ones. Just ensure your VS-REP is running before the demo starts.
The QR code is essentially a "permanent link" to your running app. As long as the server is up, anyone with that QR code can always access the latest version. Think of it like a website URL - the content updates, but the address stays the same.
If you've been away for a while, your VS-REP may have gone to sleep. Simply click "Run" to wake it up, wait for the server to start, and the existing QR code should work again.