How to Enable or Disable Spell Check in draw.io Desktop

Spell check in draw.io desktop is controlled by the enableSpellCheck Electron store setting, defaults to enabled on macOS and disabled on Windows/Linux, and requires a window reload to take effect.

The draw.io desktop application implements spell checking through Electron's native spellcheck web preference, managed entirely within the main process. This feature persists user preferences across sessions using electron-store, allowing developers to customize or programmatically control spelling validation behavior.

How Spell Check Works in draw.io Desktop

Main Process Implementation

In src/main/electron.js, the application initializes the spell check state by reading from the persistent Electron store. The logic evaluates the enableSpellCheck key, applying a platform-specific default that enables spell checking automatically on macOS while leaving it disabled on other operating systems unless explicitly configured:

// src/main/electron.js – default value (lines 82-84)
const isMac = process.platform === 'darwin';
let enableSpellCheck = store != null ? store.get('enableSpellCheck') : false;
enableSpellCheck = enableSpellCheck != null ? enableSpellCheck : isMac;

Window Configuration

When the main BrowserWindow is instantiated, the boolean value is injected into the webPreferences object. This configuration determines whether Chromium's built-in spell checker is active for that window:

// src/main/electron.js – window creation (lines 185-186)
webPreferences: {
    preload: `${__dirname}/electron-preload.js`,
    spellcheck: enableSpellCheck,
    contextIsolation: true,
    // ...
}

Default Behavior by Operating System

The spell check feature exhibits platform-specific defaults according to the jgraph/drawio-desktop source code:

• macOS: Enabled by default because isMac evaluates to true, leveraging native macOS spelling dictionaries
• Windows and Linux: Disabled by default unless the user has previously enabled the setting via the menu

This design ensures macOS users receive immediate native spelling validation, while users on other platforms must explicitly opt-in.

How to Toggle Spell Check

Via the User Interface

Users can toggle spell checking through the application menu:

1. Select Edit → Spellcheck
2. The menu sends an IPC message to the main process
3. The application updates the store and recreates the window to apply the new spellcheck flag

Programmatic Toggle Using IPC

Developers can trigger the same toggle from renderer processes by emitting the 'toggleSpellCheck' channel:

// Renderer process (e.g., custom plugin)
const { ipcRenderer } = require('electron');

function toggleSpellCheck() {
  ipcRenderer.send('toggleSpellCheck');
}

The main process handles this message in src/main/electron.js (around lines 991-992), inverting the current state and persisting the change:

// src/main/electron.js – toggle handling
enableSpellCheck = !enableSpellCheck;
store.set('enableSpellCheck', enableSpellCheck);

Reading and Setting Spell Check State

To query the current state programmatically, expose a handler in the main process:

// Main process addition to src/main/electron.js
ipcMain.handle('getSpellCheckState', () => enableSpellCheck);

Then invoke from the renderer:

const { ipcRenderer } = require('electron');

ipcRenderer.invoke('getSpellCheckState')
  .then(enabled => console.log('Spell check is', enabled ? 'ON' : 'OFF'));

To force a specific default during first-run initialization, manually seed the store:

const Store = require('electron-store');
const store = new Store();

if (store.get('enableSpellCheck') === undefined) {
  // Enable on all platforms regardless of OS
  store.set('enableSpellCheck', true);
}

Important: Changes to the stored value require an application restart or window reload to take effect, as the spellcheck web preference is only evaluated during BrowserWindow instantiation.

Summary

• Spell check in draw.io desktop is implemented in src/main/electron.js using Electron's native spellcheck web preference
• The feature defaults to enabled on macOS and disabled on Windows/Linux via the isMac platform check
• User preferences persist using electron-store under the key enableSpellCheck
• Toggling requires sending the 'toggleSpellCheck' IPC message, which updates the store and recreates the window
• Programmatic control requires IPC communication between renderer and main processes

Frequently Asked Questions

Where is the spell check setting stored in draw.io desktop?

The setting is stored in the Electron store (using electron-store) under the key enableSpellCheck. This persists the boolean value across application restarts and is read during window initialization in src/main/electron.js.

Why do I need to restart draw.io after toggling spell check?

The spellcheck flag is passed to the BrowserWindow constructor's webPreferences object during window creation. Electron does not support dynamically changing this property on existing windows, so the application must recreate the window or reload to apply the new setting.

Can I enable spell check by default on Windows or Linux?

Yes. Before the first run or during initialization, set the enableSpellCheck key in the Electron store to true. This overrides the default isMac check that normally disables spell check on non-macOS platforms.

How does the Edit menu toggle spell check?

The Edit → Spellcheck menu item sends an IPC message on the 'toggleSpellCheck' channel. The main process handler in src/main/electron.js inverts the current boolean value, saves it to the store, and triggers a window reload to activate or deactivate the feature.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}