Are you in Paris on Christmas day ?
Christmas is above all a family celebration, so don’t hope you will meet many Parisians on December 25th ! Everyone will stay at home, enjoying Christmas lunch ! No one in the streets, only tourists looking for nice restaurant or a café. Most of the museums will be closed (Christmas being on Wednesday, so they will be closed for 2 days as the Parisian museums are already closed on Tuesday)
What can you do ? Paris will belong to you, so take the opportunity to explore it and enjoy its empty streets and gardens, it could be magic ! : “Paris could be so wonderful without Parisians …” that is what I heard or read sometimes, an opinion I don’t agree with … although sometimes I like walking out of these overcrowded shopping streets like the rue de Rivoli !
You may explore the Marais on your own, or visit the Buttes Chaumont if it is snowing, or explore another less touristic district like Belleville (20th) (nice view over Paris from there) or the Buttes aux Cailles (13th) and maybe find there an open café…
Paris belongs to you alone ! no more to the Parisians … So enjoy it on your own !
Merry Christmas ! Joyeux Noël ! Bonnes fêtes !