Skip to main content

Live Preview

The whole point of AppX: describe an app, then hold the real thing. The preview panel gives you two views of your app — a fast web preview for quick checks, and a QR code you scan with Expo Go to run the genuine app on your actual phone.

When you apply a change, it reaches your phone in seconds. No manual rebuilds, no waiting for a compile.

Two Ways to Preview​

Web preview (instant glance)​

The center panel renders your app inside a phone frame, right in the browser. It's the fastest way to glance at layout and styling while you iterate.

It's an approximation, so a few things differ from a real device:

  • Native‑only features — camera, haptics, sensors, native gestures — aren't available here.
  • Some animations and platform‑specific behaviors render differently than on a phone.
  • Fonts and spacing can be slightly off.
tip

Use the web preview for layout and styling checks. For the real thing — accurate fonts, native features, true performance — scan the QR code and run it on your phone.

Device preview (the real thing)​

Scan the QR code with Expo Go and the genuine app runs on your phone. This is full fidelity: the same React Native app your users would get. Once connected, every edit you apply updates your phone automatically.

Connect Your Phone​

  1. Install Expo Go:
  2. Open Expo Go and tap Scan QR Code (iOS) or the scan icon (Android).
  3. Point it at the QR code in the AppX preview panel.
  4. Your app loads on the device.

The first load takes a few seconds to download the JavaScript bundle. After that, edits arrive instantly via Fast Refresh — no need to re‑scan.

If the connection ever drops, just scan the QR code again.

How Updates Reach Your Phone​

You apply an edit
        ↓
AppX writes the new code and checks it
        ↓
The update streams to your running app
        ↓
Your phone hot‑reloads — usually in seconds

Fast Refresh keeps your place: if you're three screens deep when a change lands, you stay there.

When Preview Is Instant vs. a Short Wait​

Each project runs in its own live app environment. On a paid plan you can keep it always‑on, so preview is instant every time. On the Free plan, an idle app goes to sleep to save resources and wakes automatically the next time you open the project or scan the QR — that wake takes a few seconds.

Always‑on is included on the Premium and Pro plans. See Plans and Always‑On.

You can share a live preview of your app with a teammate, client, or friend. They scan the QR with Expo Go and see the real app on their own phone — great for demos and review sessions. Custom subdomains are available on paid plans; see Plans.

You can also connect multiple phones to the same project at once — test iOS and Android together, or run a live group demo. Every connected device updates at the same time.

Troubleshooting​

QR code won't scan

  • Make sure Expo Go is up to date.
  • Increase your screen brightness.
  • Use the copy‑link option and paste the URL into Expo Go manually.

"Unable to connect"

  • Confirm your app is running (look for the status indicator in the workspace).
  • Refresh the preview with the reload icon.
  • If the app was asleep, give it a few seconds to wake, then try again.

Changes aren't showing

  • Shake your phone in Expo Go and tap Reload.
  • If that doesn't help, re‑scan the QR code.

Crashes on the phone but looks fine in web preview

  • Usually a native feature behaving differently on device. AppX often catches and reports these in the chat.
  • Describe what happened — "the app crashes when I tap the camera button" — and the AI will fix it.
Device Testing

Expo Go setup, the developer menu, and iOS vs Android debugging.

Always‑On

Keep your app awake so preview is instant every time.