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Full user review
"My go-to image viewer"
Fast. Small size: about 1 MB plus about 10 MB for the optional plugins. Robust: doesn't crash, runs in anything from XP on. Opens dozens of file formats and runs some videos. Hundreds of formats available with the free plugins. Panoramas. Slide shows. Did I say fast? Oh, and don't forget free. (But do donate if you can; it's worth it to keep Irfan going.)
What cons? Don't expect it to be Photoshop; that's not what it's for. It's not a paint program, either; it's not for that either.
I have IrfanView on every computer. I've used it for at least ten years with never a problem. It's great for quick image viewing and resizing images for e-mail or the web. Opens in less than 5 seconds on my old Pentium 4 box. You want to edit pictures? IrfanView will do a little, but Photoshop Elements is the best choice and only about $70.