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How do I resize the Firefox window to a specific pixel width (from within Firefox)?

shuttie27
shuttie27
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I need to take screen captures at a specific width. How can I set the window width, say, to 1275 pixels? Height is not important. I'd like to be able to do this from within the Firefox window itself.

I need to take screen captures at a specific width. How can I set the window width, say, to 1275 pixels? Height is not important. I'd like to be able to do this from within the Firefox window itself.

Chosen solution

  1. Open Scratchpad either by pressing Shift+F4 or clicking the Firefox button, opening the Web Developer submenu, then choosing Scratchpad.
  2. In the Scratchpad window, type window.resizeTo(1275,700);
  3. Press Ctrl+R or open the Execute menu and choose Run.
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All Replies (6)

Gingerbread Man
Gingerbread Man
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Chosen Solution

  1. Open Scratchpad either by pressing Shift+F4 or clicking the Firefox button, opening the Web Developer submenu, then choosing Scratchpad.
  2. In the Scratchpad window, type window.resizeTo(1275,700);
  3. Press Ctrl+R or open the Execute menu and choose Run.
cor-el
cor-el
  • Moderator
  • Top 10 Contributor
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This will only work if there is an XUL (chrome) window like the about:newtab page is open and selected. Such pages have elevated permissions and allow scripts to change the window dimensions.

shuttie27
shuttie27 Question owner
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Hi Gingerbread_Man, thanks for your response. I tried that and it didn't work. No effect. I have JavaScript enabled (in Tools, Options), and Allow scripts to resize popup windows is enabled. Combining your reply with cor-el's, I'm able to do it. Thanks!

Modified by shuttie27

shuttie27
shuttie27 Question owner
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Hi cor-el. Although I don't know what you mean by a XUL window, I tried the script on a new tab and it worked. So I guess it is a matter of permissions. I guess I could open a new tab, run the script, then switch back to the original tab. Thanks!

cor-el
cor-el
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  • Top 10 Contributor
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It also works with the "Tools > Add-ons" page (about:addons), so that is an alternative if the new tab page is set to about:blank (like I prefer).

It doesn't matter if Tools > Options > Content : JavaScript > Advanced > Allow Scripts to: "Move or resize existing windows" is disabled.

Gingerbread Man
Gingerbread Man
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Alternatively, you can install an extension. For example, “Web Developer” allows you to resize the window from its toolbar. It works regardless of which page is open, and it's simpler than typing Javascript code in a separate window.