Irfanview was always held in very high regard by my Windows using friends, not open source but freeware that's been around for at least a decade; a quick google just now seems to show that people still think it's great. https://www.irfanview.com/

If I remember correctly I've started using it in 2000s so it's around way more than that! Great piece of software that I install as one of the first things on a new Windows machine.

Agree, it's a really fast and lightweight software even in folders with thousands of photos.

It's definitely on the list of "Must Install" after a fresh OS install, with VLC and a few others.

https://nomacs.org/ fast, gpl3, native, multi plattform and sponsored by German universities.

>Preferably something lightweight and open source.

If you're already on windows (imageglass doesn't look cross-platform), why not use the built in photo viewer? It's pretty lightweight. It's not open source, but if it's already part of the operating system I don't think that's something to worry about.

https://www.tenforums.com/tutorials/14312-restore-windows-ph...

Windows 10 LTSC doesn't come with a built in photo viewer

I've searched long and hard for a fast and gpu-accelerated image viewer for Windows and settled on Pictureflect Photo Viewer last summer. Not open source, but it has both free and paid versions (with not much difference, mainly thumbnails and video playback) and it's available both on Windows Store and from their website.

I've had good experiences with XnView on Linux even though it's proprietary.

What's wrong with EOG or Gwenview?

Gwenview is pretty great, if there are builds for your platform then I highly recommend it. It's always been the perfect balance of well-designed and feature-filled for my uses.