Isofix vs. Car Seat Belt

What's the best Car Seat fitting

Car seats for infants can be attached using Isofix fittings or seat belts. But how do you decide which is the best option? We’ve set out the pros and cons below to help you make up your mind.

Whichever method you choose, remember that it’s absolutely crucial to instal your car seat correctly. The seat must be firmly fixed to the car to help restrain your child and minimise the chance of life-threatening


Seat belt method


  • It’s safe if installed properly
  • It’s flexible – not all cars have Isofix so it’s easy to switch your car seat between cars.


Top Tip

The car seat must be installed correctly to be safe. Always follow the user manual or ask an expert retailer to show you what to do.

The seat belts in some cars offer a more robust connection enabling a safer installation. Where possible, choose a car with the most suitable seat belts for a car seat.

Top Tip

Choose a car seat that clearly shows how the seat belt must be positioned. This will reduce the risk of incorrect use.


  • Up to eight in ten inexperienced parents instal their car seat incorrectly when using a seat belt. This dramatically reduces the protection offered to your child in a crash.


The most common mistakes are not pulling the belt tight enough, or leaving the belt twisted. It’s also easy to make a mistake if the car seat has no obvious way to fit the belt through it.

Top Tip

Remember that people who are not used to handling the car seat, for example a babysitter or grandparent, are at most risk of fitting it incorrectly.

Go to belt based car seats.


Isofix method


Most cars manufactured over the past ten years have Isofix fittings. This means that you can quickly click an Isofix car seat securely into place without the need to use a seat belt.


  • Safety tests show that it’s extremely safe, providing a strong and rigid connection to the car frame.
  • The risk of incorrect installation is low – 94 per cent of parents use Isofix correctly.
  • It’s fast and easy: just one click attaches the car seat solidly to the car.
  • An extra support leg or top tether strap increases stability and minimizes forward movement, keeping your child securely in place.
  • Booster seats can be permanently secured using Isofix.


Top Tip

Some Isofix car seat options, such as FamilyFix, have an LED display to confirm correct fitting for extra peace of mind.


  • Not all cars have Isofix. Check the car fitting list to see if yours has.
  • Some Isofix seats cannot be installed using a seat belt, offering less flexibility.
  • Isofix seats are often more expensive than belt-based seats due to the construction and reinforced materials needed to make it super safe.
  • An Isofix seat generally weighs more than a belt-based seat, although this isn’t always the case.


Top Tip

You may wish to buy a car seat that can be installed using either Isofix or the seat belt method for maximum flexibility – if so, make sure you choose one that can be installed both ways.


More car seat safety tips


Go to Isofix car seats and get an answer on what is Isofix?