I am trying to create a ‘For Sale’ post and I cannot upload photos. I’ve tried from two different browsers on my computer and receive the same error each time:
“Sorry, but we couldn’t determine the size of the image. Maybe your image is corrupted?”
Running Windows 11. This has only come up recently. This happens when using the “Upload from computer” or from drag-and-drop into the text area. Any site admins aware of this issue?
Try a different format ?
Touch the files with a different graphic editor ?
In the meantime you can open it under windows,
make a copy of the screen area with the screen capture tool,
Win+Maj+S, or under the notification area in W10
(probably the same on W11) and paste it in your message on Elektronauts.
Did you make the photos with an iPhone? Those default to the HEIC file format, which isn’t as widely supported supported by 3rd party software. Can you convert to a JPG? (Or turn off the HEIC mode on your iPhone and remake the photograph).
I tried two different formats; png and jpg. Going to try @simonbradford 's method when I get back to my computer.
I did but I open them in ‘Photos’ in Windows 11 and save them to a common format. I’ve tried both jpg and png. I’ve also only recently run into this issue.
Cool. Use JPG for photos. PNG wasn’t designed for the information density of photographs.
Are you resizing them? Modern cameras and iPhone make massive files. 4000px x 3000px (bigger actually). I keep photos I share online down below 1600px for the longest dimension, unless it’s an especially high res platform. Some photo viewers let you control the quality level of an exported JPG. You can get away with quite a lot less than “best” on a web forum.
Not resizing them as it’s never been an issue. Again, I’ll try a few things when I get back home. 
I just uploaded photos using an iPhone and Safari on mobile. everything worked flawlessly.
maybe try the same.