Men's dress code in restaurants in France. Should I bring a suit jacket?

I'm confident you'll be fine without it. If you've already reserved a few spots, they should note any dress code in their info. But being outside the big cities is less formal, as well as not dining in the upper range of stars, as well as I think most newer restaurants tend to be less formal, following the modern trend.

Fancy restaurants that require a jacket usually say so on their website.

And to be honest, they usually have a couple of jackets on hand that they will "make" offending customers wear if they are serious about the jackets-only policy.

No you don't need it. We dined in most of the towns you mentioned and others. There were a few men wearing jackets, but very few. I wore khaki's and a sport shirt and felt fine. Dressing respectfully honors the restaurant but no need for a jacket unless they specifically require one. Did not see any guys in tank tops and flip flops (which is distressingly more common here in California) and I hope that is not next.

We have eaten at Michelin star restaurants that require a jacket, but they make it clear when you reserve. My husband always travels with a nice blazer that he wears out and about in cooler weather and to dinner, the opera etc. But I have noticed at even nicer restaurants a fair number of men in shirt sleeves, particularly in summer, so if you don't want to carry a jacket, you will get by fine. We had dinner in a nice but not Michelin star restaurant last week in Paris and about half of the men wore jackets and others were in shirts.

Thank you for all of your help. I will now have more room in my luggage!

Depends on how you want to be perceived and treated. so I have an old Orvis Navy blue sports coat that is impossible to wrinkle. With zippered and hidden pockets it doubles as my "travel vest" on flights so I don't have to pack it.

I find a simple blazer to be a very useful garment. Goes with everything, adds tone to toney places, adds warmth, has pockets.

Aside: Do Europeans wear khakis? I don't think so.

Nicer jeans will probably be the norm (for men) in the places you plan to go.

Well then, I sure don't want to stand out as a tourist with my 27 other RS tour mates, so I guess I'll abandon the khakis I've been wearing to Europe for 10 years. And I suppose I'll be shopping for a Speedo this week. Hope my wife and daughter will be OK with that....

ALL Europeans, of ALL ages and of ALL demographics, in ALL restaurants dress how? I thought i had observed some pretty significant differences between Istanbul, London and Budapest and between a street cafe and a Michelin Star restaurant and between Budapest's District VIII and London's Kensington. Admittedly I cant recall having seen a lot of khakis in Europe: so? I think trying to look like a local is silly. Look clean and appropriate is more important. I wear parts of my homelands native costume from time to time when in Europe. They see me for what i am and it starts conversations.... Not bad at all.

Aside: Do Europeans wear khakis?

Of course. You'll see all colors of trousers on men in Europe.

At least some Europeans wear khakis. I'm married to one who does - all the time.

Khakis are what AMericans think of as dressy casual pants. They are not dressy pants in Europe and men don't wear them much. More do now than 20 years ago, but they are still not the go to dress casual look that Americans have. Dark jeans are much more likely to blend in especially with a blazer.

I've never bothered taking a jacket to Europe, and that's never been a problem even in more "upscale" restaurants. If a restaurant has a mandatory jacket (or tie) requirement, that tells me that I probably can't afford to dine there so I'll go elsewhere. My usual travel wardrobe does consist of Khakis, and that's never been a problem.

Dark blue or black jeans are not appropriate in hot weather. This advice might fly in cold weather, though.
Europeans wear white, beige, khaki, red, green, blue, yellow...this includes men (and even women) of all ages in the Summer.

Chexbres, the French wear khaki? Civilation is doomed. Do the French really dress like Moldovans?

I see a lot of sports coats with jeans and a button up shirt. The perfect shoe in May seemed to be white Stan Smith tennis shoes. You wouldn't feel out of place if you brought a nice coat that's on the casual side. It's not a necessity however.

Well, we know that the Turkish police wear khaki when they visit Washington. At least when they are beating up people.

I always travel with an unconstructed sport coat to spiff up whatever I am wearing in the evening. I usually find myself overdressed compared to most, which I don't mind. That and the lack of a backpack is why I think I have a lot of people asking me for directions and assuming I speak the language. I thought I want to blend in but it actually got old on my last trip.

I always wear my wool blue blazer to Europe. This last trip I was rarely out of it. The first week in May, in Paris, was windy, cold & damp just about every day. My old wool jacket turned out to be the ideal garment. I wore a thin, light merino t shirt, an oxford button down, a crew neck sweater & the blazer was the last layer (plus a wool scarf around the neck & over the chest, tres chic). I was comfy when most folks were in parkas.