Towing capacity
The maximum weight a car is approved to tow, listed in its handbook or specification sheet. Under UK guidance, no train weight on the VIN plate means do not tow.
Towing capacity is the heaviest load the manufacturer approves the car to tow: a rating set by the manufacturer, not a measure of what the engine could physically drag. In the UK, most cars have a maximum towing weight listed in the handbook or specification sheet, and the gross train weight on the vehicle's VIN plate is the fully loaded car plus the fully loaded trailer, which must not be exceeded. If the plate lists no train weight, GOV.UK says the vehicle should not be used for towing.
Caravanners should match trailer to rating before falling in love with a car. Check the specific trim and market, because ratings are listed per vehicle.
Towing also changes the energy math. A trailer adds weight and drag, which can raise fuel use in a gas car and cut range in an EV. Budget for that before planning a long trip with a trailer.
Differs by market
UK guidance says most cars have a maximum weight they can tow, usually listed in the handbook or specification sheet. Ratings are quoted in kilograms or pounds depending on the market; check the rating for your market's version of the car.