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Safety and breakdowns , Buying a used car , Travel and everyday · Updated 2026-10-18

Child seats: the basics

A child seat is one of the most important safety items you will buy for a car. In a crash, a correctly fitted seat can greatly reduce the risk of serious injury, but a badly fitted one protects far less. Rules on age, height, weight and front-seat use differ by country, so check them with the competent authority. This guide covers the principles that apply almost everywhere.

Match the seat to the child

Seats are designed around the child's size and weight, and the labels and manuals tell you which child they suit. Types vary between height-based and weight-based approvals, so read the label of the seat you consider. In general, there are three stages:

• Rear-facing seats for babies and small children. In a frontal crash, the seat supports the head, neck and back. Keep children rear-facing for as long as the seat allows, because it is safer for young children whose neck and head are still developing.
• Forward-facing seats with a harness for older toddlers and young children, held by the car seat belt or a fixing system.
• Booster seats for older children, which raise the child so that the car's adult seat belt fits across the strong parts of the body: over the middle of the shoulder and low across the hips.

Do not move a child to the next stage too early because they look big or are uncomfortable; check the limits on the seat. Do not buy a seat to grow into, since a too-big seat does not protect well.

Check that the seat fits your car

Not every seat fits every car. Seat belt positions, seat shape and the fixing points differ. Before you buy, ask to try the seat in your car, or check a compatibility list from the seat maker. Things to look for:

• The seat sits firmly against the car seat, with no large gaps.
• It does not tilt or rock sideways more than a few centimetres where it is fixed.
• The belt path is clear and the buckle is not hidden or twisted.
• With the rear-facing seat, there is room in front of it, so the front seat can still be set in a safe position.

Check the approval label on the seat, which shows it has passed recognised safety tests. Seats without such a label should be avoided. See understanding the data plate if you need to know your car's markings.

Fixing systems

Seats are fixed either with the car's seat belt or with a dedicated fixing system, often called Isofix, which clips onto anchor points in the car. Some systems add a support leg or a top tether for extra stability. Follow the instructions exactly. Many errors happen at this stage, so read the manual of the seat and the car's manual, and ask a trained fitter at a shop or a safety organisation to check your installation if you are unsure.

Harness and positioning

• Straps should be snug: you should not be able to pinch a fold of strap at the child's shoulder.
• Straps should be flat and untwisted.
• Remove bulky coats and snowsuits before buckling in; they compress in a crash and leave slack. Put a blanket over the child instead.
• Do not put anything between the child and the harness except what the maker approves.
• Adjust the harness height as the child grows, following the manual.

Front seat and airbags

Rules for using a child seat in the front differ by country. A rear-facing seat must never be used in front of an active front airbag, because the airbag can cause serious injury. In general, the rear seat is the safest place for children. If you must use the front seat, follow the car's manual and the local rules, and switch off the airbag only if the car allows it and the manual says so.

Buying a second-hand seat

A used seat can be a sensible way to save money, but it carries risks you cannot see. We recommend buying second-hand only from someone you know and trust, who can confirm the seat's history.

• Never use a seat that has been in a crash, even a minor one. The structure may be damaged without visible signs.
• Check for cracks, worn straps, missing parts and a missing manual.
• Check the approval label and the manufacture date. Plastic ages, and makers usually give a recommended lifetime.
• Make sure it is the seat type that suits your child and your car.

Ask yourself if the savings are worth the risk. Sellers who hide a crash history are a real concern, see scams and fake ads for related warning signs.

After an accident

After any crash, replace the child seat unless the maker says it can stay in use. Check the manual for the maker's advice, and ask your insurer whether the cost of a replacement is covered. See what to do after an accident.

Everyday habits

• Never leave a child alone in the car; heat can build up very quickly, see the summer heat checklist.
• Do not allow children to take off the harness while you drive.
• Secure loose objects, as they become dangerous in a crash.
• Take breaks on long trips; see driving with kids and pets.
• When you buy a car, think about how child seats fit before you decide; see the used car buying roadmap.

What to remember

• Choose the seat by the child's size and weight, and keep rear-facing as long as the seat allows.
• Test the seat in your car before you buy.
• Fit it exactly as the manual says, with a snug harness and no bulky coats.
• Never put a rear-facing seat in front of an active airbag.
• Avoid second-hand seats with an unknown history, and replace seats after a crash.
• Check local rules with the competent authority.

Beginner Checklist Child seat Family Safety Used car