XnView Software

Same problem as with MP 0.31.

all three IPTC/XMP Editor multi-selection options set (cochées), mode = XMP only (instead of mode = XMP & IPTC)

photo1 has the keyword A
photo2 has the keyword B

I want to add the keyword C to both photo1 and photo2 at the same time.
So I select photo1 and photo2 and I do ctrl I. But I am unable to get :

photo1 with the keyword A and C
photo2 with the keyword B and C

I get A & C (or B & C) for both photos.

How I can do it ?

You means 'IPTC/XMP edit' dialog?
Do you have click on 'clear' before?

Yes and yes.

I cleared XMP/IPTC fields for both photos and then I added keyword A to photo1 and then I added keyword B to photo2 and then I tried to add keyword C to both photo1 and photo2 at the same time (i.e. selecting both photos and calling IPTC/XMP Editor).

right a if you use XMP only!

Please check XnViewMP v0.33