Firefox users have probably come across the feature that causes the browser to automatically resize images being directly viewed so that they fit in the current size of the browsing window. It’s enabled by default after all. As you adjust the window size the viewed image will dynamically scale up or down in dimensions so that the image is always displayed in completeness.

A non-typical example, as the image is already small in size, can be demonstrated with the Google logo. Here we can see the image displayed in it’s normal 1 to 1 ratio.

However if you begin to resize the browser window, Firefox will scale down the image dimensions so that it still fits on screen. Handy for some, annoying for others.

There does not exist a preference option in the interface to change this behavior but with a big of sleuthing in about:config the setting is discovered.

Open about:config via the address bar.

In the Filter field search for browser.enable_automatic_image_resizing - their will be just one preference returned. Double click on the result to toggle the value from true to false.

The change is applied immediately without any browser restart necessary.