Genève / Geneva to Basel / Bâle by train

There are no longer any direct trains between Geneva and Basel.
Instead simple as can be connections are provided between trains at Biel/Bienne station.

You need to take trains on route IC 5 from Geneve to Biel/Bienne and connect there for trains on route IC 51 to Basel
When you arrive at Biel/Bienne the train on to Basel will be waiting on the other side of the platform/gleis, so the connection is step free.

Book early and save: Yes - If you book Supersaver tickets (more info is available on the SBB ticket guide below)

You may need to search through the departures to find them using the ‘earlier’ and ‘later’ buttons; the Supersaver tickets tend to sell out particularly quickly on this route.
The Supersaver tickets can also be more likely to still be available if you are happy to change trains.

Online bookings open: up to two months ahead of the travel date

Try and be flexible with your departure and arrival times, book as near to 60 days ahead as possible,

Look for the end-to-end journey times of around 2hr 38min, those are the journeys via Biel/Bienne.

If you will be making a day trip to Basel from Geneve be open to the possibility that Saver Day Passes can be a cheaper option than booking return tickets.

Seat reservations:

You can book reservations online, AFTER you have booked a ticket, by using the SBB (Swiss national railways) seat reservation service OR request and pay for a reservation when booking at a station ticket office.
The late afternoon and evening trains between Geneve and Biel/Bienne can be busy, but you won't need a reservation for the Biel/Bienne to Basel trains.