When you visit a website in Firefox version 100 and above, its appearance changes to match your browser's theme. Activate the “Enable custom personas” checkbox and click OK.Please update your version of Firefox for the latest features and security updates. To create a custom theme without submitting it to the Mozilla themes website, install Mozilla’s official Personas Plus extension. Restart your browser after installing it, click the Personas Plus icon on your toolbar, and select Preferences. Repeat this process if you want a footer image, but make sure it’s only 3000×100 instead of 3000×200. You can now save it to your computer (File > Save in Pixlr). You’d then crop your image - select Image > Crop in Pixlr - and you’d end up with a correctly sized image. (Of course, you could also resize your image before cropping it in this way.) You could then select an appropriately sized area of the image. Many desktop image editors (like the excellent Paint.NET) can do this, as can online image editors (like the convenient Pixlr Editor).įor example, in Pixlr, you’d open your image, select the rectangular selection tool, select “Fixed size” in the Constraint box, and enter a width of 3000 pixels and a height of 200. With a sufficiently large image found, all you need to do is crop it to the current proportions. You’ll want an image of at least 3000 pixels wide in size to start with. Footer Image: 3000 pixels wide x 100 pixels tall, PNG or JPG format, 300 KB maximum file size.Header Image: 3000 pixels wide x 200 pixels tall, PNG or JPG format, 300 KB maximum file size.Here are the exact image specifications required:

As you resize the browser window, more of the left side of the image will become visible. Mozilla advises that “Subtle, soft contrast images and gradients work best highly detailed images will compete with the browser UI.” The top-right corner should also have the most interesting bit of the image, as the top-right corner of the image will always be displayed in the top-right corner of your browser.

First, find a good-looking image that will work well on your top toolbar.

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