ISOFIX, as we have said, is designed to be a standard system for fixing child seats into cars without having to use the adult seatbelts. Unfortunately, it has taken a long time for manufacturers to develop and agree the standards, so there are currently 2 variations. 'Universal' and 'Semi-universal' or 'Vehicle Specific'.

What's the difference?

Both systems have two latches at the back of the child restraint prevent it from moving forwards, but if the car's seat cushion is soft then the child restraint can tilt forwards in a crash. To stop this forward rotation a child seat requires a third point of attachment. This will either be a rigid support leg (or foot) between the front of the child seat and the floor of the car or a 'top tether' strap connecting the top of the child seat to a fixing point on the parcel shelf, boot floor or seat back.

To be ‘Universal’ ISOFIX requires three anchorage points – two sockets where the car seat cushion meets the back and one behind the seat that connects to the top of the child restraint to stop it rotating forwards.

'Semi-universal' seats have the two sockets at the back of the car seat cushion but not the third anchorage point to hold the top of the child seat. Therefore, they often require a support leg or other 'Anti-rotation' device to be used. Child seats with two-point ISOFIX will have been tested and approved for use in specific car models and will come with a model application list.

Always ask your dealer whether an additional top tether on the seat is needed. On seats which have a 'foot' that extends to the vehicle floor, check it does not rest on the cover of an underfloor compartment.

Can I use ISOFIX?

The best way to know if your vehicle will accept an ISOFIX seat is to check your handbook or ask your local dealer. If this is not possible, you can tell by inspecting the car itself. ISOFIX anchorage points (where fitted) should be clearly labeled. You can also check along the crack between the back seat cushion and the back rest, and also on the boot floor behind the back seat.

All new cars introduced since early 2006 have been required by law to be fitted with ‘Universal’ ISOFIX anchorages for a minimum of two seating positions, however, many cars built before 2006 were fitted with the two-point 'Semi-universal' ISOFIX system.

How do I select the right seat?

If you are looking to buy a child seat to fit in your vehicle, the following manufacturers have websites that allow you to check which of their seats are suitable and/or approved for specific cars. Other manufacturers may also have a similar system.

Britax Fit-finder   ||   Maxi Cosi seat selector   ||   Recaro Isofix base or Monza Seatfix.

Additional Information.
In addition to the two main systems, there are various sub-classes, as follows:

A	ISO/F3	Full height forward facing toddler child restraint
B	ISO/F2	Reduced height forward facing toddler child restraint
B1	ISO/F2X	Reduced height forward facing toddler child restraint
C	ISO/R3	Full size, rearward facing toddler child restraint
D	ISO/R2	Reduced size rearward facing toddler child restraint
E	ISO/R1	Rearward facing infant child restraint