No it isn't, there are big posters up at the gateline at Chester station about the non functionality of contactless there.
You need a ticket - be it physical or an on line ticket.
You can from Liverpool to Ellesmere Port, but not from Chester.
As an aside don't buy tickets from a TfW machine anywhere in North Wales, as they only sell the most expensive tickets for a journey.
One day this week I ended my day at Rhyl rather than starting it there and was surprised not to be offered a walk up Advance back to the English border at Shotton, but assumed they were sold out unusually. On!y later did I find out they weren't. I paid twice as much as I should.
The day I went to Bangor I used an Advance Flex Return from Chester (a walk up fare, where you specify the outward train but can use any return train). I bought that at Warrington on the Avanti machines once I knew I was on time into the area. I checked at Bangor and couldn't have bought it there (other than on line of course). The offered fare was twice as much.
So in north Wales buy from the Clerk, or on line if no Clerk is there. At Rhyl I had a 5 minute connection from the Traws Cymru bus into train so had to make a quick decision.
There is even a button which says "choose cheapest fare". What if means is cheapest fare I sell!!
I also checked the machines at Llandudno Junction, same story.
A case of once bitten, twice shy. Now I know.