By default, IrfanView supports all the major image formats. It also supports various non-image formats natively; for example, text files. It is possible to add support for even more formats via plugins. What all this means is that IrfanView will attempt to display many files that are either unsupported, non-image or both. If you attempt to open an unsupported file in IrfanView, you will see the following error message.
With unsupported files, you have the option of installing the plugin mentioned in the error message, thus adding support to the file type in question. If you prefer not to do that then it is probably better to stop IrfanView from attempting to decode the file type. It is possible to control exactly which formats it should attempt to display.
Options ➾ Properties/Settings ➾ Extensions. You can also use the shortcut p
If you want IrfanView to load only the images associated with it, choose the option: Load only associated types while moving through folder. The Load custom file types option allows you to specify exactly which file types IrfanView must try to load. Remove the file extensions which you want IrfanView to skip over. In case you want to reset the changes you made, click on the option Load default extensions.