Yes, you can book an extra seat on EasyJet, but the process must be handled correctly to ensure the airline doesn't cancel the "empty" seat as a "no-show." Passengers often do this for extra physical comfort, to keep a fragile musical instrument in the cabin, or for religious and medical reasons. To book, you should select two passengers during the online booking process. For the second seat, you must enter the passenger name as "EXST EASYJET" (EXST is the industry code for "Extra Seat"). It is a high-fidelity rule that you must still pay the full fare, taxes, and any baggage fees for that second seat, though you do not receive a second cabin bag allowance. Crucially, both seats must be on the same booking reference. If you simply buy two tickets under your own name, the system's "duplicate booking" filter might cancel one. By using the "EXST" designation, you signal to the gate agents and crew that the seat is intentionally occupied by "space," preventing them from giving it away to a standby passenger if the flight is overbooked.