I'm on Windows and I often receive photos from iPhones in the HEIC format. Though I can convert them, it's annoying to have to do that just to view the dang photo. Is there a FOSS program that can open them without converting them? Something like VLC which pretty much handles all video formats.

I've tried downloading the HEIF Image Extension but that does absolutely nothing.

nomacs would fit the bill. The website says it can read HEIC files.

Irfanview is another option if closed-sources freeware is acceptable.

nomacs sounds neat and does RAW.

It's amazing that Irfanview is still around 30 years later and doing it's ONE THING so well still. Sure, it looks a little dated these days and can feel a bit obtuse, but it's an invaluable piece of software.

Nomacs seems to work perfectly! It even has some photo editing built in which is a nice bonus. Thanks for the recommendation!

"Looks a little dated" is just a pessimistic way to say "they haven't fucked with the ui for no reason".
I use it exactly because it still looks like it did 20 years ago.

Oh, for sure. I'm not offended by it, just stating fact.

Nice. Didn't know nomacs