Small Daypack or Purse in Paris Musuems

Most museums around the world ban backpacks/daypacks/backpack purses because you could knock into a piece of art by accident. If you have a backpack purse, you will be asked to wear it as a purse from one shoulder only.

I didn't see anything on the Louvre page about not bringing in backpacks, though of course I could be mistaken. On their website they state the following -

"It is strongly recommanded not to bring suitcases and luggage to the museum. Only luggage not exceeding 55 cm x 35 cm x 20 cm will be accepted." That breaks down to 21.6 in x 13.7 in x 7.8 in.

That luggage that 'will be accepted' mean accepted in the check room; the Louvre now has self chosen lockers to store things in rather than a manned left luggage. You can't wear a backpack and a large pack would not be allowed even worn as a purse over the shoulder. Purses and camera bags and such are not a problem. The lockers are not very big but a medium backpack would probably fit in some of them. Amusingly all the lockers when you enter the room are for motorcycle helmets and they have to have a guard full time to make sure people don't use those lockers for other things.

The size purse and day pack you mentioned would be fine, because they are about the size of a magazine.

Just try not to fill up either with unnecessary items, like bottled water and food. The less stuff you can carry into a museum, the better.

Your bag sounds similar in size to my "manpurse" (good for camera, guidebooks, umbrella; with shoulder strap) which was no problem in Paris museums. We did see a young man with a sizable backpack (no one would disagree that it was effectively "luggage") turned away at the Musée de l'Orangerie. In his case, he wasn't even permitted to check it inside -- effectively barring him from entry.

My husband and I just spent a week in Paris. I have a messenger bag and he has a small backpack he uses as a day bag. He was always asked to check his bag. All of the major museums we went to in Paris (Pompidou, Louvre, Orsay, Roudin, Cluny) offer free bag checks so you might as well just head straight there when you get to the museum because it is so easy. One small museum we stumbled into (Delacroix) needed a one euro coin which we got back when we were done.

I'm pretty sure I was able to carry my Civita day bag, which contained my camera, through the Louvre, Orangerie and Orsay museums in 2015. I had to check it at the Cluny and Picasso museums.

FWIW If my husband and I are carrying a messenger bag (we trade off carrying it on day trips) which is fairly good sized or back when we used a day pack, we found that if I carried it over a shoulder like a purse we always got in -- if he carried it on his back or over his shoulder he was usually asked to check it. These things read as luggage or backpacks when men carry them and as purses when women do. I also really recommend carrying as little as possible. Since I decided I would not carry a purse when traveling my travel has been much more pleasant. I buy clothes with hidden pockets and have reconsidered how much stuff I lug and never use. when we need to carry stuff for a day trip -- lunch, water, sweaters, we simply share one messenger bag so we can trade off carrying it and both of us don't have to be weighed down the whole way. You will be surprised how easy it is to carry the bare essentials and you can always buy a bottle of water or an umbrella if you misjudge.