I've finished most reservations of "must visit" restaurants for upcoming trip but am interested in bistros and more casual neighborhood type options. I understand food is highly subjective but would love suggestions of places that folks found and really enjoyed.
Staying in the 1st but open to Marais, St. Germain; doesn't have to be traditional French food.
TIA.

Google "Les Frenchies" + "Paris bistros". If you have not encountered Les Frenchies before, they are a husband and wife team who research and present different aspects of tourism mostly in Paris, but also some other French locations. They do a lot with good experiences in bistros, so I am sure you will find something that takes your fancy there.

Lavandula

Thanks, Lavandula. I did see a youtube video they did of 5 or 6 places. Good starting point.

Would you let us know where you booked?
I have not been in Paris in at least ten years so am just curious....the places I thought were good are probably tourist traps by now!!

Hungryonion.org has great restaurant suggestions and trip reports. David Lebovitz (his books about Paris are wonderful) has great suggestions at Davidlebovitz.com.

Our last trip we enjoyed Parcelles in the 3rd and Kubri in the 11th. Le Servan is an old favorite as is Breizh cafe. The Marche des Enfant Rouge, a covered market in the 3rd has some great casual spots to eat.

On our last trip to Paris (a 10-day trip three months ago), we found two real winners among the several restaurants we tried. First: The Armani Caffe at 149 Blvd St Germain (across the street from Deux Magots). Food was superb, as was the service. The cafe shares its kitchen with the Armani restaurant, which recently earned its first Michelin star. We had lunch there twice during our 10-day trip -- would have gone a third time but they were fully booked. Our second favorite was the brasserie at the Hotel Lutetia (43, Blvd Raspail): also terrific food and welcoming, friendly service. We did eat there three times. Great cocktail menu as well.

We're going back to Paris for a week in spring and will definitely dine at both of those again. FWIW, no dress code but people were nicely dressed at both places.

A sampling: Some Mich *'s - Alliance, Alleno, Pierre Gagnaire & Alain Ducasse. A few we have been to before: Le Christine, Boutary. New ones to try: Poulette, La Regalade, Aldehyde....
We are staying for an extended time so a number of days to fill in. Although I'm looking forward to some cooking in nights.

Thanks, WeisserTee. We stayed near Armani last trip and passed it almost every day but never tried it. Have been considering for this time so thanks for the positive. Have not been to Lutetia in over 30 years so will take a look. Much thanks.

Thanks, macdogmom, I've heard of Parcelles and will revisit the menu. And hungryonion is a great suggestion. I always forget that site

It’s kind of the Chowhound replacement and many people went there after CH shut down. There’s a poster SF Carole who goes to Paris every year for a month and has great trip reports and great taste in non touristy food.

Love this..discussion of great Paris dining right here on Fodors!!

I don't go to France much but I like HungryOnion for Spain and Italy, although I wish more people would contribute...liker the good old days of Chowhound.

After many visits to Paris we have our favorite restaurants.

We added Le Bistrot d’ Henri to the list. Small place near Blvd. Saint Germaine with excellent food. Check out photos & menu and reserve.

https://www.yelp.com/biz/le-bistrot-d-henri-paris

Thanks, TPAYT. I will look into it. I realize I had read your posts of your last trip with your lovely family. Beautiful photos of the Citroen tour and Le Train Bleu!

Run the coast, in addition to the good advice you're getting here, I would encourage you to ask your question on hungry onion. I loved chowhound but have been very disappointed in hungry onion because there is so little activity.

I pressed reply too soon. I wanted to add that I think you will get some good suggestions from hungryonion and it will juice up that forum. If hungryonion were livelier, maybe some of the old regulars would return. They are much missed.

There’s still some good content and suggestions for Paris. A couple of regulars still post. Good thread going right now.

This is another good resource.
https://parisbymouth.com

Both places will probably require reservations. Below: the cafe gourmand (cappuccino and mini dessert sampler) at Armani.

I was searching through HO and there is lots of info, Found a couple of SF Carole reports that another mentioned here. Reassuring to see places I’ve been and some of my new selections mentioned.
Looking forward to this more and more although I’m not sure how many restaurants my waistline can manage…

Le Temps des Cerises is always a delight in the Marais. I've also heard good things about Chez Janou.

I almost hate to second Le Temps des Cerises. It is such a wonderful little spot I don't want too many people to discover it!