XnView Software

Downloaded jpg images often result in "Format of the file <filename.jpg> could not be determined For displaying of less common formats, the following option is available: Options> General>[x] Display all image file types"

Thumbnail cache cleared
Program reinstalled
Ini file renamed
I DO have Display all image file types checked.

I can open the image in IrfanView; if I then save it in the same jpg format, the saved image will then open in XnView Classic.

Why is this happening and how can I fix it?

I'm running v. 2.52.0 & Windows 11 24H2

Best to post an example JPEG file that doesn't open in XnView software, if necessary in a ZIP archive, forum maximum attachment size 2MiB, otherwise you could provide a download link.

Attached is the image in a zip file

Probably not actually a JPEG, changing the extension it doesn't seem to be a PNG, I think Irfanview has an option to open incorrectly formed files, doesn't it?

white-wine-day.jpg is actually an AVIF.
This format is not supported by XnView Classic.
But XnView MP can read (and write) them.

Many content management systems convert JPEGs and PNGs on websites to WebP or AVIF without changing the filename extension.

XnView MP:

1. Go to Tools → Settings… → File list
2. Deactivate Recognize only by extension.
3. Set Scan file headers to Always