We will be in Paris next week. I've been scouting the website and doing a "dummy" request to try to see when to go online to get tickets, and it's always hit or miss, usually miss.
Hi slbdaisy (and anyone else reading this thread!)
The first batch of new time slots is released at midnight (Paris time), for the date 2 days ahead. For example: At midnight (Paris time) on October 1st, time slots are released for October 3rd. Any dates beyond October 3rd will automatically be greyed out/appear to be full. This first batch can fill up within ~20 minutes of being released, so I recommend opening the reservation system around 11:50pm. For the fastest connection, I recommend accessing it on your computer using Chrome.
A second batch of new/additional "same day" time slots are released 4 hours in advance. For example: At 5:00am (Paris time), new time slots are released for 9:00am for that same day. At 5:30am, new time slots are released for 9:30am, etc. However, there are certain hours when no time slots are ever offered, therefore no new time slots are released 4 hours in advance of those hours. For example: No time slots are offered for 12:00pm, therefore no new time slots will be released at 8:00am. The availability of these time slots is based on the planned and/or current capacity available inside the cathedral, and are not guaranteed.
Time slots are offered in 15 minute intervals. This is meant to help spread out the flow of visitors coming in/out, but it doesn't mean that you're limited to only 15 minutes to visit!
Monday to Saturday, time slots are generally offered between 9:00am and 10:45am and between 1:00pm and 4:00pm. On Thursday, additional time slots are generally offered between 7:00pm and 9:00pm.
On Sunday, time slots are generally offered between 1:00pm and 3:00pm.
Not every time slot will be offered every day, and no time slots are offered during Mass times. Visitors are still allowed to enter outside of the time frames that time slots are offered, and during Mass by waiting in the "Access without reservations" queue, which is on the left side of Notre Dame (if you're facing it), and is marked by blue signage/banners. However, priority entrance is given to those who are attending Mass/services, and pilgrim groups, school groups, international diplomats/government officials, etc (who book their time slots/reservations on a different reservation system and/or with Notre Dame's management team directly!).
The main floor of Notre Dame is open from 7:50am* until 7:00pm during the week (until 10:00pm on Thursdays), and from 8:15am until 7:30pm on weekends.
Please note that for the unforeseeable future, the ambulatory (the back half of the cathedral) and the back chapels don't open until 8:45am during the week.
Everyone has be out before closing time and the ambulatory (the back half of the cathedral) and the back chapels close at 30 minutes before closing time, so I recommend entering at least 1 hour before closing time.
For the lowest crowds, I recommend visiting on Tuesday, Wednesday or Thursday before 10:30am.
Or, if you're available on Thursday evening, I recommend visiting between 7:00pm and 9:00pm (the ideal time to visit is around 8:30pm). This is generally a more peaceful time to visit! Notre Dame is open until 10:00pm on Thursday, but everyone has to be out before 10:00pm and the ambulatory (the back half of the cathedral) and the back chapels close at 9:30pm, so I recommend entering at least by 9:00pm.
