How to Change Themes in FastStone Image Viewer

FastStone Image Viewer is a free and fast loading image viewer for Windows. It supports all the known image formats, many digital camera models and offers a host of image editing and management features. Now starting with the version 7.5, it comes with three themes – dark, bright and gray. These themes can be enabled to match FastStone Image Viewer window with the dark or light modes of Windows 10 user interface.

Unfortunately like many other applications that offer similar themes or modes, FastStone Image Viewer has no options to automatically switch to the dark or bright theme if Windows 10 has been set to use the dark or light mode. You have to manually enable any of these themes in FastStone Image Viewer in the following manner:

  1. Launch FastStone Image Viewer from its desktop shortcut.
  2. Select Settings from the menu bar, then Themes and then you can choose bright, dark or gray themes.Change Themes in FastStone Image Viewer
  3. This is it, the themes are applied instantly.

The dark theme is almost black and looks very much like the dark mode of Windows 10 user interface. The bright theme is the default theme and shows the interface in a much more modern style. The gray theme looks like the older color settings from Windows XP times.

If you are using an installed copy of FastStone Image Viewer in Windows, then its settings are saved in the user profile folder for the user who is currently using the computer. In case of a portable version of FastStone Image Viewer, the settings are saved inside the same folder where the FSViewer.exe is located.

Unlike some other popular image viewers, FastStone Image Viewer does not allow any custom third-party themes or icons for its toolbar. It would have been much better if they allowed users to edit the themes and share the user created themes online.