What's the latest on Airbnb in Paris?

The highest court in Europe, the European Court of Justice, has (in September 2020) ruled in favor of Paris city authorities rules that have made tax registration obligatory for apartment owners and have restricted those renting out their primary residence to a maximum of 120 days a year. These apartments when listed on the internet must have 13-digit registration number beginning with 75. The rules for those who own second homes are more restrictive. In order to rent a furnished property for less than a year to vacationers, owners must apply to local authorities for permission to change the registered use of the space. They are then required to buy a commercial property of an equivalent or bigger size and convert it into housing as compensation. There are about 120 (maybe it's 150) registered vacation rentals in this second category. Basically, there are still vacation rentals out there that are not compliant with these rules and there are rentals that are compliant. You can find both on AirBnb. Booking.com, to my knowledge, only lists apartments with the 13-digit registration number. Some agencies continue to list apartments without a registration number. People I know who live in Paris full time expect that post-pandemic, there will be even fewer vacation rentals than there were last year and last year there were significantly fewer than there were five years ago.

I prefer Airbnb, but there are other sites, even Booking, that offer apartments. Given the reply above, I checked a couple of Airbnb listings and they include the registration number.
I have rented in other cities with registration requiremenrs and the reputable hosts either have it on the listing or provide it on request.

I just went to the official website that lists the second category of apartments that I mentioned in my first post --- currently, there are a lot more than 150. The site is https://tinyurl.com/kb38mxjx.

The key court ruling was just a few months ago on February 18th. This is the final decision, there is no further appeal. Basically the courts sided with city of Paris, fines may now be collected (a backlog of over 400 fines of up to 50,000€ per offense) and enforcement will recommence. Here is an article (in French) which explains the February decision.

Basically, there are two broad categories of legal short term apartment rentals:

1. Commercial apartments of which there are about 500 in Paris. It is very expensive to qualify commercial apartments, most of these rent for about the price of a 4 star hotel. Nice has different rules for this category.

2. Private apartments which are the owner's own principal residence, rented while he is away. Annual rentals are limited to 120 days in Paris, 90 days in Nice.

There is a newer classification called a mobility lease which can, under certain circumstance, allow owners to rent apartments for only a few months. I don't have a lot of information on the mobility lease, but it was designed for those who need temporary housing while they are looking for an apartment, changing jobs, or perhaps changing marital status.

Apartments without registration numbers clearly visible in any advertisement are offered illegally. However, the inverse is not necessarily true, that all registered apartments are guaranteed legal to rent. The owner of a registered apartment may have already rented it for the 120 day annual maximum, or an owner might have registered his secondary home which is possible to do but not legal to do. As enforcement efforts by the city start up, many of these questions will be resolved. The city will eventually confirm that all registrations numbers are properly issued.

There is no proof positive method to assure a visitor that his vacation rental accommodations are without issue, Be careful.