Ordering champagne in Paris

Do cafes, bistros and restaurants in Paris ever serve champagne by the glass or is it always by the bottle?

You can get champagne by the glass in many (most) places indeed. Champagne is an ingredient in the typically Parisian drink kir royal, so there’s always a bottle open.

Merci, Jovan.

Depends. In the little cafe where I just had a coffee moments ago, Champagne won’t be sold by the glass, plainly because it’s unlikely that another customer will want one before the champagne is spoiled. So, you can forget about “kir royal” except if you intend to order a bottle. On the other hand, it will certainly be possible to order a glass of champagne in very busy bars, in large “brasseries”, etc…
So, you’ll have to ask. IMO, most places wouldn’t serve champagne by the glasss. The different perception Jovan has perhaps come from the fact he came to Paris as a visitor, hence tended to visit more centrally located and busy cafes, while at the contrary, I tend to have a drink in little “corner of the street” cafes…

Yeah, I think I got a bit overboard with “most,” although I think that most bars as opposed to cafés would have a large enough turnover to at least advertise it on their menu - in busier areas. Still, the concentration of bars, brasseries and cafés is such that you shouldn’t have any problem finding a place that does serve it by the glass.

Just ran across to road to test the theory and 2 cafes already had a bottle open and said fine but the other said no as they probably wouldn’t be able to see much more today (a ‘normal’ kir is cheaper!).

As the others said ‘most’ cafés will wive you a glass as long as they’re in tourist or populated areas and most brasseries (bars that serve food).