React Native iOS, in the browser

Run React Native simulators in your browser

100% client side… no Mac, no XCode, no VM!

SootSim is a brand new, clean-room React Native simulator that runs entirely in your browser, making development faster, cheaper, and easier (especially with agents!).

DownloadLive demo →Docs ↗

npm i -g sootsim

Use Cases

Develop

Point sootsim at any Metro server and your unmodified bundle just works — hot reload, and all.

0 native build. Mac, Linux and Windows.

Validated on Bluesky, Uniswap, Expensify, Artsy.

No streaming — even runs in iOS Safari.

One-click to record flows as shareable preview links — a truly usable and real live app + video recording.

Watch, pause, and step inside at any point.

Entirely client-side — no server bridge.

Preview

SootSim PR bot studies what changed, creates a Maestro flow, and posts an inline video + real live demo in minutes.

Test-drivable preview link in minutes.

Inline webm video — no leaving the PR.

Test

Detox and Maestro files run completely unchanged, now your CI is as cheap as headless Chromium on Linux.

No build step.

Regression assurance for pennies.

Keep iOS sim for final-mile parity.

Features

10x CLI

Agents connect, control, and debug in a fraction of the time of the iOS Simulator, with smart React Native context.

Automatic sessions, waits for animations, screens.

80+ React Native-aware actions with better context.

Automatic error surfacing, screen-aware info.

Instant Start

Every simulator is just a browser tab that starts instantly with no build. Run as many parallel as you want instantly.

No rebuild, no reboot, many devices.

Cold loads in seconds, runs completely local.

No streaming lag, no Mac in the cloud.

Show off

Three ways to share your app: live preview recordings, app store screenshots, and 3D demos.

Record yourself using an app, get a shareable link with a video + real usable demo in seconds.

Screenshot Mode for easy app store screenshots.

3D Mode for amazing social media demos.

Refine

Inspect-to-prompt in seconds with the built-in agentic devtool designed for faster feedback loops.

Inspect → prompt iteratively in seconds.

Claude Code and Codex integration.

Smart context/prompt tuned for speed.

Engine

Multi-worker

Your bundle, the shell, and the page each run on their own thread — same semantics as React Native.

Animations, scroll, and gestures stay smooth when JS is busy.

Lists cull, repaints stay contained — close to native iOS.

Real Reanimated

Real Reanimated code, real UI vs main thread runtime semantics. No polyfills involved.

Shared values, animated styles, layout animations — device-faithful.

Gesture Handler on the same runtime — pan, pinch, swipe feel native.

Pixel-perfect iOS

Status bar, Dynamic Island, keyboard, alerts, sheets, picker, notifications, control center, app switcher, home, lock — all built on pixel-diffing.

Apple emoji, SF Pro, P3 color — pixel-matched to iOS.

Pro, Pro Max, SE, mini, iPad — exact pt sizes and safe areas.

Surprising compatibility

220+ native modules work, stubbed against real browser APIs. 350+ pure-JS libraries compose without a shim.

Reanimated, Gesture Handler, Screens, FlashList, MMKV, WebView, Vision Camera, Skia, Notifee.

Real iPhone vs sootsim, pixel-diffed side by side. See /compat.

Verified Compatibility

Core

99%

Top 100

84%

Top 500

69%

top 500 native libraries by weekly downloads

verified

works

partial

not yet

How it works: Validation of popular native packages. We don't validate JS-only packages beyond a few high value ones as most "just work" due to high Core conformance.For native packages, we use unit and integration testing to estimate a baseline. Then, for React Native and other high value packages, we also run true pixel-diff. The final score combines both.

react-native

the framework itself · 81 pixel-checked surfaces

99%

react-native-gesture-handler

DrawerLayout (passthrough noop), NativeViewGestureHandler still lacks native-scroll coupling and handlerTag semantics, cross-detector simultaneousWithExternalGesture/requireExternalGestureToFail, ForceTouch semantics are placeholder-only

99%

react-native-screens

freezeEnabled/enableFreeze (always false), statusBarColor/navigationBarColor/navigationBarTranslucent ignored, replaceAnimation differentiation, formSheet detent fidelity, integrated search bar placements

99%

react-native-svg

SVG filter primitives (Filter, FeBlend, FeColorMatrix, FeGaussianBlur, FeComposite, etc) — all fe* skipped; ClipPath/Mask/Use/Pattern/Symbol/Image listed as skipped in engine

99%

react-native-reanimated

layout animation builders are exported but no enter/exit animation actually plays, useScrollViewOffset returns static 0, useAnimatedSensor static, useReducedMotion always false, useAnimatedKeyboard height tracking returns 0

99%

react-native-keyboard-controller

per-frame keyboard progress events (smooth `onMove` requires SAB-backed shared values driven from the shell-side keyboard animation; deferred — see plans/real-worklets.md)

98%

react-native-keyboard-controller sootsim

All Packages(8 of 642)

expo-linear-gradient

CanvasKit gradient shader via _gradientColors style prop, full API

100%

react-native-pager-view

overdrag (accepted but ignored), offscreenPageLimit (accepted but ignored), pageMargin, keyboardDismissMode, native scroll fidelity (momentum physics differ)

94%

expo-image

transition/animation effects, placeholder rendering, blurRadius, contentPosition, sfEffect/SFSymbol, allowDownscaling, autoplay (GIF), responsivePolicy

92%

expo-video

player.duration stays 0 (no timeupdate listener), player.currentTime not synced from element, statusChange/volumeChange/timeUpdate events not emitted, useEvent hook not exported, DRM support absent

89%

react-native-webview

actual web content rendering inside the canvas worker, onShouldStartLoadWithRequest, allowsBackForwardNavigationGestures, userAgent, dataDetectorTypes, cacheEnabled, incognito, scalesPageToFit, canGoBack/Forward in iframe-mode (always false), originWhitelist enforcement

55%