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How do I set the general zoom level programmatically

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  • Igcine ukuphendulwa ngu jscher2000

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When I use Firefox on the external monitor, I set the zoom level to 150%. When I leave home a take my laptop with me, I set the zoom level to 100% to use with a smaller screen.

I want to automate setting the zoom level.

Is there a way to programmatically set the zoom level from a script? Does Firefox expose such an API / command-line tool?

Thanks!

Isisombululo esikhethiwe

Hi Pierre, this is a tough one. The default zoom level is stored in a database with site-specific zoom levels, and there's no preference you can set directly to modify that value.

You definitely can do it with a script you run manually in the Browser Console window, which has an optional global command line. The Options page is probably faster...

/* Default Zoom Level Setter for the Browser Console (2020-08-12)

   NOTE: BEFORE YOU CAN RUN THIS SCRIPT, ONE-TIME SETUP:
   Type or paste about:config into the address bar and press Enter
   Click the button promising to be careful
   In the search box type devt and pause while Firefox filters the list
   If devtools.chrome.enabled is false, double-click it to toggle to true

   Paste this entire script into the command line at the bottom of the Browser Console 
   (Windows/Linux: Ctrl+Shift+j; Mac: Command+Shift+j). Then press Enter to run it. 
   Firefox should flip to an open window and ask what percentage you want.
   
   Ref. https://searchfox.org/mozilla-release/source/browser/components/preferences/main.js#1166
*/

var newpct = window.prompt('New default zoom percentage (e.g., 100, 120, ...)?', '150');
if (newpct){
  let cps2 = Cc["@mozilla.org/content-pref/service;1"].getService(Ci.nsIContentPrefService2);
  let nonPrivateLoadContext = Cu.createLoadContext();
  let win = window.browsingContext.topChromeWindow;
  cps2.setGlobal(win.FullZoom.name, parseFloat((newpct / 100).toFixed(2)), nonPrivateLoadContext);
}
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All Replies (1)

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Isisombululo Esikhethiwe

Hi Pierre, this is a tough one. The default zoom level is stored in a database with site-specific zoom levels, and there's no preference you can set directly to modify that value.

You definitely can do it with a script you run manually in the Browser Console window, which has an optional global command line. The Options page is probably faster...

/* Default Zoom Level Setter for the Browser Console (2020-08-12)

   NOTE: BEFORE YOU CAN RUN THIS SCRIPT, ONE-TIME SETUP:
   Type or paste about:config into the address bar and press Enter
   Click the button promising to be careful
   In the search box type devt and pause while Firefox filters the list
   If devtools.chrome.enabled is false, double-click it to toggle to true

   Paste this entire script into the command line at the bottom of the Browser Console 
   (Windows/Linux: Ctrl+Shift+j; Mac: Command+Shift+j). Then press Enter to run it. 
   Firefox should flip to an open window and ask what percentage you want.
   
   Ref. https://searchfox.org/mozilla-release/source/browser/components/preferences/main.js#1166
*/

var newpct = window.prompt('New default zoom percentage (e.g., 100, 120, ...)?', '150');
if (newpct){
  let cps2 = Cc["@mozilla.org/content-pref/service;1"].getService(Ci.nsIContentPrefService2);
  let nonPrivateLoadContext = Cu.createLoadContext();
  let win = window.browsingContext.topChromeWindow;
  cps2.setGlobal(win.FullZoom.name, parseFloat((newpct / 100).toFixed(2)), nonPrivateLoadContext);
}

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