UPDATE 2:

Use webFrame.setZoomLevelLimits (v0.31.1+) in render process (Differences Between Main Process and Renderer Process). Because smart zoom on mac still work with document.addEventListener.

Example require('electron').webFrame.setZoomLevelLimits(1, 1)

UPDATE:

deltaY property for pinch zoom has float value, but normal scroll event return int value. Now solution has no problem with ctrl key.

Demo 2.

document.addEventListener('mousewheel', function(e) {
  if(e.deltaY % 1 !== 0) {
    e.preventDefault();
  }
});

Using Chromium monitorEvents(document) I found that is responsible for this event mousewheel. I don't know, why mousewheel triggered with pinch zoom. Next step, find difference between normal scroll and pinch zoom.

Pinch zoom has an attribute e.ctrlKey = true, and normal scroll event has e.ctrlKey = false. But if you hold down ctrl key and scroll a page, e.ctrlKey equal true.

I couldn't find a better solution. :(

Demo

document.addEventListener('mousewheel', function(e) {
  if(e.ctrlKey) {
    e.preventDefault();
  }
});

It seems very difficult for desktop browser to prevent pinch zoom.

Here are some ideas though!

1) By using some gestures javascript like hammer.js, detect Pinch event and try to prevent it using e.preventDefault

OR

2) Design everything using "%" in css, or use newer units like "vm" etc, (if possible). This way, even page will be zoomed, but content will stay the same for any zoom level.

All the best!

Answer from GitHub:

"If you are looking for a way how to prevent zoom from main process, you can use:"

const webContents = mainWindow.webContents;
webContents.on('did-finish-load', () => {
  webContents.setZoomFactor(1);
  webContents.setVisualZoomLevelLimits(1, 1);
  webContents.setLayoutZoomLevelLimits(0, 0);
});

mainWindow is variable where you have new BrowserWindow, e.g.:

const mainWindow = new BrowserWindow({
  width: 440,
  height: 750,
  // ...
});

const webContents = mainWindow.webContents;
webContents.on("did-finish-load", () => {
  webContents.setZoomFactor(1);
  webContents.setVisualZoomLevelLimits(1, 1);
  webContents.setLayoutZoomLevelLimits(0, 0);
});