Captions and Google Photos working with XnView

[Weberpa]

I'm noticing some weird things with captions and Google photos and wondered if anyone had advice. If I add a caption using XnView to a photo that is in a folder that is synced to Google Photos it does not update the the caption that appears in Google Photos. But if I upload the photos manually the caption will appear in Google Photos.

Inversely, if I have photos in Google Photos where I add a caption in Google Photos, then download the the photo and open it with XnView it does not appear.

Any advice on this? Ideally I had hoped that XnView captions would automatically upload to Google when added to photos in synced folders, and that Google photos with captions downloaded to my computer would show their captions in XnView.

Apologies if I'm not stating this clearly enough, it is an odd thing I've noticed in uploading and downloading photos.

thanks for any advice,
Paul Weber

[xnview]

could you post an image file where caption is not recognized by Google Photos? And one recognized?
I think that Google Photos use XMP and not IPTC metadata