EasyJet describes their seating policies on their website: Whilst our seating system will always try to seat families together, seats are allocated on a first come first served basis so the earlier you check in the more likely you are to be seated together.

EasyJet’s automated seating algorithm will attempt to sit passengers on the same booking together, but it is not a guarantee unless you pay for seat selection. If you choose the "free" option and wait for the system to assign seats during check-in, the system looks for groups of adjacent seats. However, if the flight is nearly full, your party may be split up. For families traveling with children under 12, EasyJet has a specific policy to ensure that at least one adult is sat next to each child at no extra cost, though the system may still split the adults in a larger group. In 2026, with load factors consistently high, travelers who are anxious about sitting together are strongly encouraged to pay the small fee (typically starting at £5.99) to reserve their seats in advance. If you decide to gamble on the free allocation, checking in as early as possible—up to 30 days before departure—is the best way to increase your chances of being sat together before the cabin becomes "checkerboarded" by paid reservations.