What is ISOFIX?

If you have children, or are planning the arrival of your newborn, you will likely have come across the ISOFIX term when researching car seats.

ISOFIX is an internationally standardised car seat system which most modern cars have incorporated into their models.

The system was named at the International Organisation for Standardisation – aka ISO.

How does ISOFIX work?

In terms of it’s application, the ISOFIX system is a very secure way for your car to lock a child’s car seat in place when driving.

Within the car itself, if it is ISOFIX compatible, you will find anchor points within the point of the seat where the seat meets the back rest. These are usually metal and u-shaped.

Car seats which have the ISOFIX system included in their design have either metal or plastic arms with corresponding clips at the end of these arms.

You position the car seat in place and then push these clips into the anchor points where the clips attach. This secures the car seat in place and it can only be disengaged by the use of buttons on the arms which release the clips.

Baby seats usually have a 3rd point of contact with the vehicle in the form of a ‘leg’ which extends to the case of the footwell.

With baby seats the child is then strapped into the seat with integrated harnesses within the seat.

For toddlers and young children, depending on the design, their car seats usually make use of the car’s seat belts to strap them into the car sear.

How do I know if my car has ISOFIX?

It is highly likely that your car will have ISOFIX installed as part of the car’s design. The system has been a standardised since 2006 and a legal requirement in the UK since 2014.

The best way to check if your car has ISOFIX though, is to physically check. Go out to your car and feel between the gap that connects between the car seat and back rest of the rear passenger seats.

You should be able to feel the metal u-shaped bars that make up the anchor points for the ISOFIX system.

Some cars even have a plastic container that goes around the metal bars, making it extremely obvious where the ISOFIX points are located.

Is ISOFIX safer than a seatbelt?

Older car seats, before the introduction of ISOFIX, used to rely on the seat belt of the car looping through the child seat to secure it in place.

ISOFIX is a safer way of anchoring the car seat as it ensures that the car seat is secured in a standardised way. With seat belts there was always the risk of it not being looped or secured too loose by the user.

With a mechanical element, this risk is mitigated. It also means that the metal anchor points and clips on the seat provide a much more robust and secure way to holding the seat in place.

Most ISOFIX systems have a warning light on them, so if they are not installed correctly you will see a red light and hear a small alarm.

This ensures that each time you use the system it is working correctly before you set off.

How to fit an ISOFIX car seat

The first time you install an ISOFIX car seat may seem daunting, but it is a generally easy thing to do. As long as you take your time and not try to force it.

1. Find the anchor points in your car for the ISOFIX. Some of these may be hidden behind a cover. If you are unsure where they are, then you can check your vehicle handbook.
2. Place your car seat, or car seat base, into the back seat – aligning it up with where the ISOFIX anchor points are.
3. Extend the arms on the car seat/base and slowly push the anchor arms into the ISOFIX connectors. You should feel a little resistance followed by a ‘click’ sound when they connect correctly.
4. Make sure the back of the child seat is firms against the backrest of the car seat. The arms can be shortened if the car seat is sticking out too far.
5. If your child’s car seat also requires the seat belt of the car be used to secure the child, make sure that this is loose and put through any parts of the seat as required.
6. If your ISOFIX base or seat has a support leg, make sure this is extended and firmly in contact with the floor of the car.

ISOFIX age range

As the ISOFIX is a mechanism designed to secure child seats in cars, rather than a specific type of seat itself, it can be used with child seats for different age groups.

That is until a child is legally allowed to use a standard adult seatbelt—either when they reach 135cm in height or turn 12 years old.

In general, child seats are categorized into five groups:

• Group 0: Lie-flat baby carriers suitable for infants up to 10kg.
• Group 0+: Rear-facing baby carriers for infants up to 13kg.
• Group 1: Rear or forward-facing seats for children weighing between 9-18kg.
• Group 2: Rear or forward-facing seats, as well as high-backed booster seats, for children weighing 15-25kg.
• Group 3: Rear or forward-facing seats, as well as high-backed booster seats, for children weighing 22-36kg.

The specific group should be selected based on your child’s age and weight, ensuring compliance with legal standards.

To view the latest UK laws, visit the .gov website.