Day Trip to Ravenna from Venice

IMO too far for a day trip
Train will take 3.5+ change in Ferrara
Driving not much better, probably 2.5+
Just doesn’t give you much time in Ravenna
There are multiple mosaic sights, all within walking distance of each other ( not counting the ones that are out of town)
I think you’d be crunched for time

I do see a Frecciarossa train departing Venice at 9:26 that gets you to Ravenna in 2 hours 12 minutes, with a single change at Ferrara. That station is really easy, and that is not a bad journey time for a daytrip. But it may be dat3e dependent so check for your actual travel date.

Note that the ticket procedures have changed for the sites with the mosaics. Two of them you have to have timed entry and they are strict on the entry. Personally I don't think a day trip from Venice is a good idea. Ravenna is a great place to visit and I would spend more time there if possible.

If you are debating a day trip from Venice versus at least one night in Ravenna, then more time is much better. If the only way you will ever see the mosaics in your life is as a day trip from Venice, then it will be a complicated, rushed day but worth it.