By default, Firefox is so coded that it resizes large sizes images and extremely large size pictures to fit them inside it windows, this is called auto thumb nailing in Firefox. The size of the Firefox depends on which monitor you use. For users who have small-sized picture tube this can be quite annoying to display full size image and extra-large size images.
Right now what all Firefox users does is open the image and click on the image to see the full size image. Actually this is done by Firefox itself, interesting you can modify this feature. If you would like to view the high quality pictures as they are in their original size here is the trick to prevent Firefox from thumb nailing of your pics.
1. Type about:config in the address bar and press enter you will be taken to configuration page.
2. Now it will warn you whether you want to proceed or not since you are about to enter modifications tricks where you would be able to modify details which change alter changes to browser performance, stability and security. It’s safe to click on ‘I’ll careful, I promise‘.
3. Now in the filter field provide browser.enable_automatic_image_resizing.
4. Under the Filter field the preference should appear. Right click on it and select Toggle.
5. When you click on Toggle it will change it value from True to False which will disable automatic resizing of image. Conversely if set it to True will enable automatic image resizing.
6. It’s safe to close that tab and for the setting to functions properly restart your Firefox.