Navigo Decouverte Card

You cannot buy the Navigo Decouverte card until you get to Paris (or CDG Airport.

You may want to take the required photo (1” by 1.25”) for each of your family members.

I just scanned my passport photo and decreased its size prior to printing it.

Have a wonderful trip!

There’s a ticket buying counter (for lack of a better word) with agents selling tickets at CDG just before you enter the RER system, i guess it’s possible, but i don’t think likely, that they’d run out of the Navigo Découverte for you to buy.
It is common and normal for tourists to buy the ND, i’m sure ticket agents don’t care who you are. As Priscilla said, just have your photos with you.
I buy the ND even just for a few days because it is so easy and convenient to use, if i save money it’s a bonus.

Anybody can purchase a Navigo Découverte (5€) but it is just a card, itself it takes you nowhere. You must load a fare onto the card and there are many options. There are daily fares, weekly fares, and monthly fares. If you find that the sales window at CDG has depleted its supply of available cards, ask at the other airport location. There are two staffed sales offices, one at terminal 2 and a second at Roissypôle. The two locations are connected, as are all terminals, by the free rail link CDGVAL and both are departure points for the RER B into Paris.

When i fly into CDG after a 10+ hr flight, the last thing i want to do is traipse all over CDG and their different terminals with luggage and jet-lag to find a ticket window that has the ND card if the first ticket counter i went to had none. I’d just pay for a regular ticket. But in that case, jicohen, it is about the same price for 4 people to just take a taxi - if you don’t have too much luggage. Taxis from CDG to Paris (and back) are a flat rate - €50 Right Bank and €55 Left Bank.

What Susan said were my exact thoughts, too, particularly since there are four of you.

traipse all over CDG

There are only two locations for ND card sales at CDG, both are RER stations. It´s unlikely that cards will be sold out but there are options if that occurs.

A taxi may be similar in price to 4 RER tickets but purchasing 4 weekly Navigo fares (about the price of two airport taxi rides) will cover transportation into Paris, around Paris for 5 days, and back to the airport on Sunday.

We were originally going to take a taxi from the airport, as we will only need it inbound to Paris. However, we are thinking of going to Versaille and Montmartre and we will be taking the train to Nice, so the Navigo Decouverte weekly pass would be perfect for us. We are staying near Saint Michel-Notre Dame station and planning to use metro and RER trains as much as possible while in Paris. The ND card is good for RER B to our hotel, so why spend the extra $55 euro if we don't have to? Plus, we will be arriving late Wednesday afternoon, so I imagine traffic would be bad getting into Paris city centre.

It's good to know that both ticket sales offices are near RER B departure points. We will land in Terminal 2A and will have to go through immigration. Thankfully, no checked luggage for any of us! Where is Roissypole? Just so that I'm clear, do we purchase the physical card and the sales agent would affix the photos? And we are looking to purchase the weekly pass for that week, so will the sales agent load it onto each of our cards or do we load it at the ticket machines? Thank you for all the helpful info!

Agents, normally, will help you affix your photo and they will load the card for you.

Of course a ND is the most economical - i was saying if the ticket window has none, i wouldn’t then go to the trouble to get to the other location in another terminal. But that’s me. Happy to save money but i have my limits. Anyway, as i already said, it’s possible but not likely an agent will run out.

It would be pretty odd for the RER stations at CDG to not have them.

There's really no need to acquire Navigo cards in advance (but once you have acquired them from either of the RER stations at CDG, you can keep them for future trips to Paris, and load new fares onto them from automated machines).

Given that you are flying in on a Wednesday, late in the afternoon, planning to visit Versailles on one day, and taking the train out early on a Sunday, you might save a bit with:

• single magnetic RER tickets from CDG (free transfer from the RER to the Métro en route to your destination),
• Zone 1-4 Mobilis day passes (magnetic) for your Versailles day, and
• a "carnet" of 10 slightly discounted magnetic Métro tickets to share, and/or Zone 1-2 Mobilis day passes, for your remaining days.

The benefit, apart from a small potential savings, is that all of these fares can be purchased from automated machines. Carry a pen to write the date on Mobilis day passes.

If you want the Navigo Découverte, bring appropriately-sized photos (dimensions given by another poster) to save time and money. Navigo Découverte only benefits you if you will make future trips to Paris, or if the cost of the card and the all-zone Monday-Sunday weekly pass ("Forfait Semaine Toutes Zones") that you would be loading onto it is less than the combined cost of the fares I listed above. Later arrival times and earlier departure times reduce trip counts on your first and last days, and departing Paris by train reduces the number of high-zone trips (although Versailles might compensate).

If you find that the all-zone Sunday-Monday weekly pass doesn't pencil out but you still want to try Navigo, consider Navigo Easy as an alternative to Navigo Découverte. Navigo Découverte requires a photo and can be loaded with Monday-Sunday weekly passes and day passes, whereas Navigo Easy has no photo and can be loaded with day passes, single Métro tickets, and 10-ticket "carnets" (though the benefit of sharing one carnet among multiple people is lost). On each Navigo Découverte card, you would load a Zone 1-5 day pass ("Forfait Jour") at CDG (or, use a single magnetic RER ticket if not traveling again that day), load a Zone 1-4 day pass for your Versailles day, load Zone 1-2 day passes for other days, and load a single Métro ticket for your last day (or, use a single magnetic ticket that day, or share a "carnet" of 10 magnetic tickets and forego one of the Zone 1-2 day passes).

Worth noting: a Forfait Jour loaded onto a Navigo Découverte or Navigo Easy card costs the same as a Mobilis magnetic day pass, but Mobilis is never valid for airport trips, even if it covers high zones. At the time you load a Forfait Jour onto a Navigo Découverte or Navigo Easy card, you must specify the travel date. You can prepurchase a few days in advance, but you cannot change the date after loading. Mobilis, on the other hand, is totally flexible: you just write the date before using it.

For future readers: magnetic tickets are slowly being phased out.