Are wheeled backpacks allowed as airline carry-on luggage?

Several models in this category are marketed as carry-on or underseat compliant, but airline size limits vary by carrier and route. Verified-purchase reviewers consistently advise checking your specific airline's dimension caps before flying, since the wheel housing and retractable handle add bulk that can push a bag over the limit. The larger 50L-and-up options are generally check-bag size, not carry-on.