Can anyone recommend a small, fast image viewer that handles lots of formats, especially AVIF, WebP, and HEIF? I just need it to view images and nothing else.
I’m really fed up with ACDSee, it’s super bloated, takes forever to load, and has this annoying tray app that runs every time Windows starts.
I use and recommend IrfanView. 
Also one of my favourites. Imageglass is also excellent.
XnView or IrfanView. Both free, both can be run portable.
Nomacs is really fast. I remember there was a test of popular image viewers, and Nomacs was the only lightweight one that showed accurate colors.
But if you want the most complete one, XnView MP is the way to go.
Check out FlyPhotos on GitHub. It’s designed to mimic features of Picasa Photo Viewer and is an ongoing open-source project.
Is this your project? It’s super fast! Thanks so much for all your hard work!
Just one thing: Sony RAW files shot vertically show up rotated sideways, so the vertical orientation isn’t respected. File Explorer and FastStone Image Viewer display them correctly (probably using the JPEG preview inside the file).
I ran into the same issue with an alternative File Explorer shell, even though the author said it shouldn’t happen since it pulls thumbnails generated by Windows’ File Explorer.
If you want, I can provide a sample file for testing.
But overall, awesome work!
It’s my project. Thanks for the comments. I shall check the orientation issue with the sample file.