XnView Software

saving in this format will discard any existing metadata!
don't ask again

This dialogue comes when:

- opening .jpg and saving as heic
- opening .jpg and saving as avif
- opening jpg and saving as jxl

This dialogue does NOT come when

- opening heic, avif or jxl? and saving as jpg

Some metadata (pic date, gps, camera lense data) seems to be still saved even the dialogue gives warning.

So is some data actually lost? I notice that this dialogue does not seem to come when using Export... dialogue.

I am considering converting my pic collection (very large, 40 000 pics from 4 decades) from jpg, maybe even .CR2, .RW to more modern file format (heic, avif or jxl) to save hardrive space

But I don't want to lose any metadata in the process and pic amount is too large to check every single pic through so I am wondering how reliable this feature is.

I am not going to do it very soon but hopefully inside 1 year or so.

I already transcoded all my jpg files into jxl files. There are two ways to do it:

1) decode the jpg files and re-coded them into jxl files with a comparable quality setting. This can be done using Xnview or cjxl.exe (under windows, downloadable from github/jxl, and there are also version for linus and macOS). This makes it possible to divide the size by 2 but at the price of some loss of quality. The loss of quality can be avoided by setting a higher jxl quality level, but then, the gain in size is dramatically reduced. The size can even increase if the quality 100 is used, because in this case, jxl faithfully reproduces the jpg image, including the jpg artifacts, and this takes a huge amount of bytes.

2) losslessly/reversible transcode jpg into jxl. The size is reduced by 20% (only, but not so bad), and the jpg file is kept intact (and can be therefore regenerated back exactly from jxl is necessary). Unfortunately, this mode available in the native cjxl has not been (yet?) implemented in Xnview. Fortunately, cjxl can be easily batched, so that it is possible to transcode thousands of jpg files with a single command

Otherwise, on my side no jxl metadata issues with 1.8.6 (the issue was present in previous versions but has been solved in 1.8.6)

it's a false warning (XMP & EXIF metadatas are kept)
Thanks to your detailed description I can reproduce the problem.

This problem is supposed to be fixed in XnView MP 1.8.7. Please check and confirm the bug fix here.

seems fixed