Paris in August

I've been to Paris maybe a dozen times, and most of those in August. I can't say I've noticed any difference.
Every major tourist attraction was open.

Small independently own mom and pop shops close. It depends on what you plan to do in Paris?

We were there last August for the second time and we actually prefer it then. The atmosphere is more relaxed and crowds, other than the popular tourist sites, are less. We arrived in August and ended our trip there in early September - the difference in the number of people on the street was remarkable, at least in the area we stayed in ( the 8th near Gare St. Lazaro) . The Louvre was still quite busy (packed) in the morning but quite light in the afternoon. Small mom&pop operations tending to take rolling vacations - I.e.not all the restaurants take the same vacation time. The closed shops/restaurants had signs, printed or hand-written, that gave the dates they would be on vacation All the places on the Champs Elysee were open and busy. Hope this helps.

A number of small restaurants with nice recommendations were closed on my last August visit -- certainly not all, but some. Live music events were scarce and only a couple of the big museums/art galleries had special exhibitions mounted. But hotel space is said to be more available than in July and (perhaps) September.

Thanks so much! I appreciate your advice and prompt response...

You didn't actually ask this but do get a hotel with AC. I've hit August in Paris in a heat wave and it can be miserable. You may need a cool retreat during the hot part of the day. Locate the nearest gelato shop to your lodging, hahaha!

I'd book a lodging where there is air-conditioning. If you want to go AirBnB, there won't be any air-conditioning.
There are many smaller stores that will take off during the week, the rest of the big department stores and restaurants stay open.
There are also parks that stay open until about 11PM or so, so the residents and tourists can take a "bonne bouffee d'air".

Agents are posted to keep out nonsense.

If this is your first time to Paris, I doubt you'd notice anything being closed. Parisians do tend to clear out this month for vacation, but it's still one of the biggest cities in the world and a major tourist destination--you'll have no problems going in August (other than a possible heat wave, but oh well!) At most you might find one very particular restaurant you want to go to will be closed, but there are thousands more open :)