What is Isofix?

What is Isofix and does my car have it?

Isofix is the safest way for a child to travel in a car, but what is it and does your car have it? Our guide has the answers.

Cazoo Editorial Team Byline Icon

By Cazoo editorial team

Published: 17 November 2022

If you’re looking at a used family car on the Cazoo website, it will almost certainly have at least two Isofix points, but what does Isofix mean and what is it for?

Well, Isofix is the most convenient – and safest – way to attach a child safety seat in a car. Isofix stands for International Standards Organisation Fix and Isofix mounts have been mandatory in all new cars sold in Europe since 2014. 

Here’s our guide to everything you need to know about Isofix.

What is Isofix?

Rather than use a seat belt to secure it, an Isofix-compatible seat clips directly into a pair of small metal Isofix hoops, or anchorage points, built into the car’s structure. Not only is this a safer and more secure method, but it also removes the element of doubt that your child is securely seated in the car.

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How do I know if my car has Isofix?

The easiest way to find out if your car has Isofix is to look for the labels on the back seats. These are normally in the form of a felt tag or a circular button, either with an illustration of a child in a seat or the word ‘Isofix’ on it. 

The labels tell you exactly where to find the Isofix mountings, which are often hidden in the gap between the seat back and the seat cushion. In some cases, the Isofix points are behind a plastic cover, which you need to lift out of the way before fitting the child seat.

You’ll also find Isofix points listed under safety and security features on every car listed on the Cazoo website. If in doubt, consult the car’s handbook or contact the customer services department of the car’s manufacturer.

Are all child seats compatible with Isofix?

Not all child seats are designed for Isofix anchorage points. Some use the car’s three-point seat belt, so this could be a handy option if you regularly transfer the seat to different cars or your car doesn’t have Isofix points.

The other thing to consider is the size of the child seat. Some Isofix-compatible child seats are big and bulky, especially those intended for older children, so they might not fit in city cars and small hatchbacks. Many retailers will allow you to test a child seat in your car before you buy it, and will also provide advice on fitting it into the car.

When did Isofix become mandatory?

Isofix has been a legal requirement on all new cars sold in the EU since 2014, but you’ll also find the mounting points on many older cars. The system was developed by Volkswagen and Britax Römer in 1997 and became popular on cars in the mid-2000s.

What ages of children is Isofix suitable for?

Child and baby seats are categorised by weight and age. There are four groups: 0, 1, 2 and 3, although some seats can span several groups. In other words, a group 1/2/3 seat is suitable for children 9 months to 12 years old and weighing 9kg to 36kg.

Isofix points are suitable for children from birth until they’re 12 years old or 135cm tall, whichever comes first, although child seats for older children (groups 2 and 3) are often referred to as Isofit. 

In a car with Isofix, the seat is mounted to the car using the anchorage points, with the child strapped in using an in-built harness. For older age groups (Isofit), the seat is attached using the Isofix mounts, but the child uses the car’s seat belt.

How do I fit an Isofix car seat?

Locate the Isofix points in your car by checking the owner’s handbook and looking for the relevant label on the back seats. The mounting points are in the joint between the back of the seat and the seat cushion. 

Then simply push the connectors on into the Isofix slots and listen for a ‘click’ sound to let you know that the seat has been securely attached. You may need to adjust the angle of the connectors on the seat if you’re struggling to attach them. If space is tight, it’s worth sliding the front seats forward to give yourself more room to manoeuvre.

You then need to make sure the seat belt fits properly – this usually involves pushing it through a clip on the child safety seat that holds the belt in the correct place. Removing the seat is usually as simple as going through  the same process in reverse.

How do I fit an Isofix seat designed for babies?

Isofix baby seats usually have an additional car seat base to use Isofix. The base acts like a cradle for the seat, which locks quickly and easily into place.

If the seat has a supporting leg, make sure it is adjusted so that the seat is braced against the floor. Be aware that seats with a supporting leg are unsuitable in cars with underfloor storage compartments. If in doubt, check the child car seat fitting and compatibility page on the website of the Royal Society for the Prevention of Accidents, known as RoSPA.

Is Isofix safer than a seatbelt?

Fitting a child seat using a seat belt isn’t necessarily unsafe, but the risk of getting it wrong is much higher. There’s no guarantee that the seat has been fitted correctly, meaning there’s a greater chance of injury in the event of a collision. Because Isofix provides a rigid connection between the car and the seat, there’s less chance of installing it wrong. It’s also more convenient and less hassle when you’re loading a child into a seat because you know the seat is secure.

Is it possible to have more than two Isofix points?

While a car with four seats must have at least two Isofix points in the back, cars with three mounting points are surprisingly common. 

Large MPVs such as the Citroen Grand C4 SpaceTourer and Citroen Berlingo have Isofix points on each of the three back seats. Some cars also have an Isofix point on the front passenger seat, while the Audi Q7 SUV has six Isofix points, one for each potential passenger.

It’s not only on big cars; the Renault Zoe electric car and Nissan Micra are available with an optional Isofix point in the front.

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