Diagonal or A-frame ski carry, back pocket for the shovel and probe, fairly flat back to sit comfortably on a chairlift: our category brings together ski backpacks, from day trips at the resort to ski touring.
Diagonal carrying is quick to set up, with a low strap and a high buckle, and it hardly hinders walking. The A shape distributes the load on both sides and keeps the field of vision clear, causing less fatigue on a long ascent. A serious ski backpack offers both, with reinforcements where the edges rub. The real test is done with gloves on, both on the attachments and the buckles.
On a chairlift, a ski backpack that is too thick prevents you from leaning back and pushes you forward in the seat. A flat back, a contained width, and compression straps solve the problem better than reduced volume. Check the position of the helmet holder, a helmet hanging behind gets stuck while boarding. For a day at the resort, a ski backpack that is compact is enough; it holds a spare goggle, dry gloves, and something to eat.
In ski touring, the ski backpack carries the skis during the walking sections and must accommodate skins, crampons, and a warm layer without having to open it fully. The back panel separates the shovel and probe from the rest of the load, it can be accessed even with the backpack placed in the snow. A ski backpack for touring also provides a compartment for a water bladder and an insulated sleeve for the hose; otherwise, the hose can freeze.