A walking harness spreads load across the chest and back, making escape less likely and suiting lead walks. A collar mainly carries ID, concentrates load on the neck, and is not a suitable anchor for a lead.

Harnesses suit cats already used to going out and needing longer walks; check the armpit opening and adjustment range, since H-style and vest-style differ. Collars suit daily ID wear, ideally with a safety release and a light tag that will not snag.

The risk is fit and adaptation: harnesses need training to put on, too tight restricts the forelegs, too loose allows escape. Collars can catch on furniture indoors, so remove them or use a breakaway clasp when the cat is alone.

Separate the functions: harness for the lead, collar for ID, and neither replaces the other. Do indoor fittings and short sessions first; if the cat freezes, shakes or pants, stop, because forcing an outing deepens stress.