Capybara

Free and open source · macOS, Windows, Linux

Debug React Native and web apps from one place

Logs, network (including WebSockets) and storage, streamed live from your app to a local UI. React Native 0.85 and later needs no SDK.

Download View on GitHub

Runs on your computer. No account, no telemetry.

Capybara's Network tab: a list of an app's requests and the JSON response of the selected one.

See what your app is doing

One window for every app on your simulators, phones and browser tabs, updated as things happen.

Find out why a request failed

Browsers only tell your app “Failed to fetch”. Capybara repeats the request's CORS steps from your computer and names the cause: a missing Access-Control-Allow-Origin, a failing preflight, a blocked port.

A failed request explained: blocked by CORS because the response has no Access-Control-Allow-Origin header.

Logs that keep their shape

Objects, Maps, Sets, Dates and errors arrive as values you can expand, stack included. Filter by level or regex, and copy one entry or all of them.

The Logs tab of a React Native app, with an expanded error and its stack.

Read and edit storage

localStorage, sessionStorage and cookies on the web. AsyncStorage and MMKV in React Native. Values refresh as the app writes them, and JSON opens as a tree.

The Storage tab showing AsyncStorage keys and a settings value opened as a JSON tree.

No SDK for React Native

On React Native 0.85 and later, Capybara attaches through Metro. Start your app as usual; nothing to install in it.

Requests and WebSockets

fetch, XHR and axios with headers, bodies and timing. WebSocket messages both ways, with socket.io frames decoded.

Ask your AI assistant

Capybara's MCP server lets Claude Code, Cursor and other MCP clients read and filter what it recorded, with credentials hidden.

Get started

Pick the kind of app you're working on.

React Native 0.85+

Works today

No SDK and no changes to your app.

  1. Download Capybara and open it.
  2. Start Metro and run your app on a simulator or phone.
  3. Your app appears, with its logs, network and storage.

Web apps

Coming to npm

Install the SDK and call init() before the rest of your app. In Next.js, put it in instrumentation-client.ts.

npm install @capybara-devtools/web
import { init } from '@capybara-devtools/web';

if (import.meta.env.DEV) init({ appName: 'My web app' });

AI assistants

Coming to npm

Let Claude Code, Cursor or any MCP client read what Capybara recorded.

claude mcp add capybara -- npx capybara-devtools mcp

Older React Native, or want to edit storage from Capybara? Add @capybara-devtools/react-native; the README shows how. Until the packages are on npm, run Capybara from source.

How it works

  1. Your app React Native through Metro, or a web page with the SDK
  2. Capybara A small server on your computer, on port 7357
  3. You The desktop app or a browser tab, and your AI assistant over MCP

Everything runs on your computer: no account, no cloud service, no telemetry.

Download Capybara

Free for macOS, Windows and Linux. Latest release on GitHub

macOS

Apple silicon (M1 or later)

First launch

Capybara isn't notarized by Apple yet. If macOS won't open it, go to System Settings › Privacy & Security and click Open Anyway.

Windows

Windows 10 and 11, x64

First launch

The installer needs no admin rights. SmartScreen may warn about an unknown publisher: choose More info, then Run anyway. When Windows Firewall asks, allow private networks so phones on your Wi-Fi can connect.

All releases Build from source Report an issue