Peeing in Paris

There are public restrooms all over the city. You can also buy a 2 euro coffee at any cafe and use the toilettes. Department stores; i.e. le Bon Marche, Galeries Lafayette, le Printemps, or the BHV all have public restrooms.

400 free public toilets. Here's the map. https://en.parisinfo.com/practical-paris/useful-info/public-toilets
As many cities, you can't expect to use a restaurant one without paying for an item. Some may also charge for TP....I recall that set up for the Seine Bateau cruise....but it also means someone is paid to keep it clean and tidy.

Since last month you can go to a listed historical monument:

"The lavatory de La Madeleine" which dates from 1905 and has reopened its doors.

It will not only be useful to you but it is also a place to visit (2€, cheaper than the Eiffel Tower)

https://www.sortiraparis.com/en/news/in-paris/articles/289538-lavatory-de-la-madeleine-the-rebirth-of-a-heritage-jewel-in-paris

If you have the Paris Museum Pass, you can pop in to any museum on the list and usually use a well maintained bathroom. You might even discover a few museums that you would otherwise never have visited!

If you use the museum pass for this, then you will have used up your visit to that museum. Since they now only allow one entry per museum, it is no longer so useful for quick drop ins.

Thank you, MariaF. I believe that will be valuable info during my trip to Paris next month.

Thanks everyone, for the great advice and information!

There is an App: Toilettes Paris.