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Embedded Simulator

The embedded simulator lives right inside Nativeline. No juggling windows, no switching apps. You build with chat on the left, and your app runs on the right.
Nativeline Build tab with embedded simulator showing a running app

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How It Works

When you open the Build tab, the right side of your workspace becomes a live simulator. Every time you make a change through chat and the build succeeds, your app automatically launches and updates in that same view. 
┌─────────────────────────────────────────────────────────────────┐
│  Toolbar                                                        │
├────────────────┬────────────────────────────────────────────────┤
│                │                                                │
│   Tabs         │   ┌──────────────┐  ┌──────────────────┐      │
│                │   │              │  │                  │      │
│   - Build      │   │  Chat +      │  │   Embedded       │      │
│   - Database   │   │  AI Responses│  │   Simulator      │      │
│   - Code       │   │              │  │                  │      │
│   - Settings   │   │              │  │   [ iPhone ]     │      │
│                │   │              │  │   [ Your App ]   │      │
│                │   │              │  │                  │      │
│                │   └──────────────┘  └──────────────────┘      │
│                │                                                │
│                │   ┌───────────────────────────────────────┐    │
│                │   │  Message Input                        │    │
│                │   └───────────────────────────────────────┘    │
└────────────────┴────────────────────────────────────────────────┘
No separate Simulator app. No window management. Everything is right where you need it.

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Getting Started

1

Open your project

Select a project from the Nativeline home screen or create a new one.
2

Go to the Build tab

Make sure the Build tab is selected on the left sidebar. The simulator panel appears on the right side of the workspace.
3

Send a message

Describe what you want to build or change. The AI writes the code and kicks off a build automatically.
4

Watch it appear

When the build succeeds, your app launches in the embedded simulator. You can interact with it immediately.
The embedded simulator updates automatically after each successful build. Just keep chatting and watch your changes appear.

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Interacting with the Simulator

The simulator responds to your mouse and keyboard just like a real device. Click inside the simulator frame and start using your app.
ActionHow
TapClick
ScrollClick and drag, or two-finger swipe
SwipeClick and drag
Long pressClick and hold
Pinch/zoomOption + click and drag
HomeCmd+Shift+H
RotateCmd+Left/Right Arrow

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Text Input

Click on any text field in the simulator and type with your Mac keyboard. The simulator uses your hardware keyboard by default.

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Device Selection

You can change the simulated device to test how your app looks and feels on different screen sizes. Look for the device selector in the simulator toolbar.
DeviceBest For
iPhone SESmall screens, compact layouts
iPhone 16Standard size, most common
iPhone 16 Pro MaxLarge screens, edge cases
iPadTablet layouts, multitasking

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Appearance

Toggle between light mode and dark mode directly from the simulator to make sure your app looks great in both. This is especially useful if your app supports dynamic colors or adaptive styling.

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Platform Differences

iPhone

Shows an iPhone simulator frame with your app running inside. Full touch interaction support.

iPad

Shows an iPad simulator frame. Great for testing tablet-specific layouts and multitasking.

Mac

Your app runs natively in a window on your Mac. No simulator needed.
When building for Mac, your app runs natively in a window on your Mac. There’s no simulator — you’re testing the real thing.

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Build States

As your app compiles and launches, the simulator area shows what’s happening:
StateWhat You’ll See
BuildingA progress indicator while your code compiles
InstallingThe app is being installed on the virtual device
RunningYour app is live and interactive
ErrorThe build failed — check the chat for details and fixes

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First Launch

The first time the simulator boots, expect it to take 30 to 60 seconds. It needs to spin up the virtual device and load iOS. After that initial boot, subsequent launches are much faster. The simulator stays warm in the background, so rebuilds appear almost instantly.

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Screenshots and Recording

While the simulator is focused, you can capture what’s on screen:
  • Screenshot: Cmd+S (saved to your Desktop)
  • Screen Recording: Use the Simulator menu to start and stop recording
These are great for sharing progress, reporting bugs, or creating assets for your App Store listing.

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What the Simulator Can’t Do

The simulator covers most of what you need for development, but some things require a real device:
Not AvailableWhat to Do Instead
Real cameraUse the photo library to test image picking
Actual GPSUse simulated locations (Features menu)
Push notificationsLocal notifications work fine for testing
Accurate performanceDeploy to TestFlight and test on a real device
Face ID hardwareUse simulated Face ID (Features menu)
For anything the simulator can’t handle, deploy your app via TestFlight and test on a real iPhone.

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Troubleshooting

The simulator can take 30 to 60 seconds to appear on first boot. Make sure:
  • The Build tab is selected (not Code or Settings)
  • You’ve sent at least one message to trigger a build
  • You’re building for iPhone or iPad (Mac apps run in a native window)
If it still doesn’t appear, try restarting Nativeline.
  • Check the chat for build errors — the AI usually explains what went wrong
  • Make sure the build has fully completed (watch for the success indicator)
  • The app may have launched to a blank screen if there’s a runtime error — check the chat for details
  • Close other heavy applications on your Mac
  • Try a simpler device (iPhone SE instead of Pro Max)
  • Restart Nativeline to reset the simulator
  • Make sure your Mac has enough free memory
  • Click directly inside the simulator frame — clicks outside it won’t register
  • Make sure the simulator has finished loading (wait for the app to fully appear)
  • If the app is frozen, send another message in chat to trigger a fresh build

Chat Interface

Learn how to build your app through conversation

TestFlight Overview

Test on real devices with TestFlight