From today, 15th November 2017, Easyjet has a new luggage policy for new bookings.
Basically it's 15 kilos now but for a bit more you can have 23kilos. You can also up it to 32 kilos if you increase by 3 kilo increments.
Prices vary depending on the destination and flight length.

https://www.easyjet.com/en/help/baggage/cabin-bag-and-hold-luggage

15kg wow if you think back Easyjet was the first main budget airline, started it all off, its not anymore though.

Taking onboard with you, a small case 55 x 30 x 20 (ish), with no weight restriction, for FREE, hasn't altered.

15 kilos is what I have in my hand luggage.