Île-de-France has 5 different pass products, none of them obvious. This picks the right one based on trip length, zones used, daily rides, and whether you need airports covered.
A 5-day Paris trip with 4 rides a day costs €84 in Ticket t+ — but only €35.20 with Navigo Semaine (zones 1-5, all-inclusive, 7 days rolling). Most travelers overpay because they don't know which zones they actually need, or they buy a Paris Visite "tourist pass" that costs 2× more than the equivalent Navigo.
The non-obvious trade-offs: Navigo Mois is unbeatable for 30+ days; Navigo Semaine starts the moment you first use it (not at midnight Monday like before); Paris Visite looks convenient but is rarely optimal unless you're flying in, out and around with no clear itinerary.
The single best product for your inputs, with total cost and rides included. Look for the % you save vs the runner-up.
"Zone 1–2" means Paris intra-muros only. Versailles = zone 3 (you need 1-3). CDG airport = zone 4. Orly = zone 4. Beauvais = no RER; you need bus + separate ticket.
Navigo Mois requires a physical card (€5 one-time). The €5 isn't included in the monthly price. Same for some Paris Visite tiers.
Navigo is subsidized as the daily commute product for residents. Paris Visite is a commercial tourist product with marketing overhead and museum discounts baked in. If you're not using those museum discounts, you're paying 2–3× more for the same trains.
No. Eurostar Paris-London is a separate ticket. But the RER B from Paris to CDG airport is covered by zones 1-4/1-5 Navigo — use that, not the expensive Roissybus.
Yes — Marne-la-Vallée Chessy (Disneyland) is zone 5. With Navigo zones 1-5 you take RER A direct from central Paris. ~45 min from Châtelet.