How strict is EasyJet carryon dimension

Well, I've only taken Easy Jet once and there were sizers at the beginning of the jetway and EVERY person had to drop their carry on into the sizer before the gate agents let them go down the jetway.

Yes. The mean what they say.

What fare class did you book? What is the size of your bag? The Standard Allowance is this 45 x 36 x 20 cm. While the other class is this 56 x 45 x 25 cm. It depends on how much you want to pay.

We had a gate agent that walked down the line of people getting ready to board and was pulling people out that had luggage that was too large. I would even think twice about bringing regular sized luggage as carry-on. I've used EasyJet twice and both times by the time it was my turn to board the overhead bins were full. I was lucky and had checked my luggage anyway.

Yes they can be very strict. It must fit in a bin of the correct dimensions.

There are 2 size limits for carry on luggage. 1st is the included underseat bag (no additional charge), the 2nd is the larger cabin bag that goes in the overhead locker (you have to pay around €30 per flight for this bag). If your bag is too big for the overhead locker measurements you’ll have to check it. You won’t be able to take it as carry on.

If your bag is too large, you'll pay a very high price at the airport; it's much cheaper to deal with an oversize bag in advance, online.