Paris shuts down early and its annoying when you need stuff after dinner around République. Here's what actually stays open:

Pharmacies with green cross signs rotate 24-hour duty, google 'pharmacie de garde paris' for current one. Supermarkets: Monoprix Champs-Élysées until midnight, several Franprix around République until 10pm, check Google Maps for hours.

Laundromats 24/7 mostly, especially near student areas in Latin Quarter and Belleville. Internet cafés still exist and stay open late around République and 11th arrondissement.

Food: kebab shops obviously around Châtelet, but also Chinese restaurants in 13th stay open until 11pm-midnight. Casino supermarket near Gare du Nord is 24 hours for international travelers.

Nothing exciting but useful when you realize you need toothpaste at 9pm and everything touristy around Louvre is closed.