---
title: Electron SDK
---

# Electron SDK

Electron SDK runs entirely in the **main process**, opening a native, OS-managed CAPTCHA window. The renderer never touches the verification — keep it that way for security.

## Demo on GitHub

::: tip 📦
[Captcha-La/electron-demo](https://github.com/Captcha-La/electron-demo) — full runnable example with every integration step.
:::

## Install

```bash
npm install @captchala/electron
```

The package targets **Electron 28+** (the demo pins `^33.0.0`) and **Node 18+**. Run the demo end-to-end with:

```bash
npm install
npm start
```

## Quick start

```js
// main.js (Electron main process — never the renderer)
const { app, BrowserWindow, ipcMain } = require('electron');
const path = require('path');
const { CaptchalaClient } = require('@captchala/electron');

let currentClient = null;

ipcMain.handle('verify', async (event, opts) => {
  // 1. Fetch a one-shot server_token from YOUR backend.
  const serverToken = await fetchServerTokenFromYourBackend(opts.action);

  // 2. Tear down any prior client, then build a fresh one.
  if (currentClient) { currentClient.destroy(); currentClient = null; }
  currentClient = new CaptchalaClient({
    appKey: 'YOUR_APP_KEY',
    serverToken,
    action: opts.action,        // 'login' | 'register' | 'pay' | …
    lang:   opts.lang,          // 'en' | 'zh-CN' | 'ja' | …
    theme:  opts.theme,         // 'light' | 'dark'
    timeoutMs: 15000,
    retryCount: 3,
    onReady: () => event.sender.send('captcha-status', 'ready'),
    onFail:  (e) => event.sender.send('captcha-status', `recoverable: ${e.code}`),
  });

  try {
    const result = await currentClient.verify();
    // Send result.passToken to YOUR backend for validation.
    return { success: true, passToken: result.passToken };
  } catch (err) {
    return { success: false, error: err.message };
  } finally {
    if (currentClient) { currentClient.destroy(); currentClient = null; }
  }
});

function createWindow() {
  const win = new BrowserWindow({
    width: 520, height: 640, resizable: false,
    webPreferences: {
      preload: path.join(__dirname, 'preload.js'),
      contextIsolation: true,
      nodeIntegration: false,
    },
  });
  win.loadFile('index.html');
}

app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
```

```js
// preload.js — bridge the renderer to the main-process verify().
const { contextBridge, ipcRenderer } = require('electron');

contextBridge.exposeInMainWorld('captchala', {
  verify:   (opts)     => ipcRenderer.invoke('verify', opts),
  onStatus: (callback) => ipcRenderer.on('captcha-status', (_, msg) => callback(msg)),
});
```

## API surface

| Symbol | Purpose |
| --- | --- |
| `new CaptchalaClient({...})` | Construct a one-shot client. Pass `appKey`, `serverToken`, `action`, `lang`, `theme`, `timeoutMs`, `retryCount`, plus event handlers. |
| `await client.verify()` | Open the native CAPTCHA window. Resolves with a result on success, rejects on hard error. |
| `onReady` / `onFail` | Optional handlers passed in the constructor. `onFail` is for *recoverable* failures (the SDK will retry). |
| `result.passToken` | The token to validate on your backend. Always opaque to the client. |
| `client.destroy()` | Close the window and release resources. Always call once you are done with a client instance. |
| `CaptchalaClient.version()` | Static helper that returns the SDK version string. Useful in support / debug overlays. |

## Server-side validation

Forward `result.passToken` (or `result.token`) to your backend and validate it against the CaptchaLa API. Never expose `X-App-Secret` in client code.

```bash
POST https://apiv1.captcha.la/v1/validate
X-App-Key: YOUR_APP_KEY
X-App-Secret: YOUR_APP_SECRET
Content-Type: application/json

{ "pass_token": "<result.passToken>" }
```

See the [API Reference](../api-reference) for the full validation endpoint and `X-App-Key` / `X-App-Secret` flow.

## Troubleshooting

- **Don't import the SDK in the renderer**  
  `@captchala/electron` is **main-process only**. Expose its result through `contextBridge` + `ipcRenderer.invoke()` like the demo's `preload.js` does. Keep `nodeIntegration: false` and `contextIsolation: true`.

- **Module not found at runtime**  
  `@captchala/electron` is a regular dependency, not a devDependency — it must be packaged into your final app. Bundlers like electron-builder include it automatically.

- **Window opens behind your main window**  
  This is a Linux/X11 quirk. Pass `parent` in your own `BrowserWindow` if you wrap the CAPTCHA window, or call `mainWindow.focus()` after `verify()` returns.

- **`Electron 28+` required**  
  The demo declares `electron: ^33.0.0`. Older Electron may miss APIs the SDK relies on; pin to `28+` and Node 18+.

## Requirements

- Electron 28+ (the demo uses 33.x)
- Node 18+
- Cross-platform: macOS, Windows 10 1809+, Linux (X11 / Wayland)