ISOFIX is a system that allows for easy attachment of child seats to a vehicle. The ISOFIX system securely and reliably connects the child seat to the vehicle’s body. Its main advantage is the simplicity of installation. Child seats with the ISOFIX system are safer due to the strong connection between the seat and the vehicle!

ISOFIX is an international designation for standardized attachment of a child seat in a vehicle. The ISOFIX system complies with the international standard ISO 13216-1, which establishes rules for attaching child restraint systems. In practice, this means that automobile manufacturers install standardized anchorage points in their vehicles, which are subsequently used by child seat manufacturers for a firm and reliable connection of the seat. ISOFIX ensures mutual compatibility.

ISOFIX system logoISOFIX system anchorage point

ISOFIX is a component of passive safety. With the advent of this system, the safety of child passengers has significantly increased, and instances of improperly installing child car seats into vehicles have been minimized. Compared to the classic method of securing a child seat using regular seat belts, ISOFIX provides a more suitable alternative for attachment.

Function Principle:

The ISOFIX system creates a solid connection between the child car seat and the vehicle’s body, thereby reducing the risk of injury to the child being transported in the seat. The connection between the child seat and the body is achieved using rigid connectors, which are firmly attached to special anchorages directly on the body or on the seat’s structure. The advantage of the ISOFIX system is the ease and reliability of use, and above all, the strength of the seat’s attachment to the vehicle.


ISOFIX system attachment diagram  ISOFIX system attachment

 the principle of anchoring child seats using the ISOFIX system

ISOFIX operates on the principle of simply clicking two locks into two prepared anchors. Proper installation of the seat is verified by a typical click and a green indicator.

Advantages of the ISOFIX System

  • safer
  • reliable seat installation

Disadvantages of the ISOFIX System

  • higher purchase cost
  • more difficult seat transfer from place to place

Child car seats are divided into several categories, and from the perspective of vehicle placement and the ISOFIX system, two methods are important:

1/ Group 0 and 0+ (0-13 kg / 0-12 months)

Infant car seats for category 0-13 kg are preferably placed with the child facing backwards. In the event of a collision, the energy of the moving child is absorbed by the entire back surface, including the head. In layman’s terms, the child’s body has nowhere to fly in a frontal collision. Since especially in small children, the size and weight of the head are disproportionately larger compared to the body, this reversed position prevents dangerous neck spine injuries.

In order to use the ISOFIX system, seats for the smallest children (so-called eggs) usually use an attachment base that is fixed to the seat. To increase the stability of the child seat, it can be equipped with an adjustable support leg.

It is recommended to place the seat in the rear, which is safer. The seat can also be placed in the front seat, but the airbag must always be turned off!!! An active airbag is deadly dangerous for a child!

car seat with ISOFIX system

 2/ Group I (9-18 kg / 9 months – 4 years) + Group II (15 – 25kg / 4 – 6 years)

Car seats for older children are placed in the vehicle facing forward. In some countries, even a small child can be placed in a child car seat in the passenger seat. Some vehicles even have ISOFIX attachment points on the front seat for this purpose. Remember, however, that the passenger airbag is designed according to the adult male model. The impact velocity and geometry are optimised for the adult passenger. The child sits in the seat in a slightly different position. He sits higher and, above all, closer to the dashboard than an adult passenger who is leaning against the headrest. For transporting a child in the front seat, transport safety experts recommend moving the whole seat and the child seat as far back as possible.

car seat with ISOFIX system

Video of installing an ISOFIX seat:


Seat belts on seats with ISOFIX system:

Even if a seat has an ISOFIX system, it does not necessarily mean it has its own belts! Higher quality seats for smaller children usually have own belts, as they help to secure the child better! In such a case, in the event of a collision, the ISOFIX system holds the seat, and the child is held by the seat through integrated child belts. These belts are typically three to five-point (number of attachments to the chassis), the more, the better for safety.

Seat with ISOFIX system  Seat with ISOFIX system + TOP TETHER

However, if a seat with ISOFIX does not have belts, the classic seat belts of your car are used to secure the children. In this case, the ISOFIX system holds the seat during the impact and the seat holds the child via the integrated child belts. These are usually three to five points (number of attachments to the carcass), the more the better for safety.

The least secure scenario is when the child car seat is without ISOFIX. In this case, in the event of a collision, the classic safety belts hold both the seat and the child, since the seat is not firmly anchored, it pushes on the child, which is not ideal.

Video installation of a seat with ISOFIX system:


In 1997, the company BRITAX RÖMER, in cooperation with the VW Group, introduced a child car seat anchoring system called ISOFIX. The name ISOFIX was created from two parts, ISO from the International Organization for Standardization and FIX from the English word fixation, meaning fixation, attachment.

The first car with the ISOFIX system was the VW Golf IV generation. Already in 1999, this system became an international standard that minimizes errors during installation and optimizes protection effectiveness thanks to the solid connection of the child car seat with the vehicle, the ISO 13216-1 standard was created.

Today, ISOFIX is a mandatory element of passive safety in new vehicles. According to current European regulations, since February 2013, all new vehicles must be equipped with anchoring points for at least two ISOFIX and TopTether child seats.


Some car seats may be equipped with the Top Tether system, which complements the ISOFIX system and further enhances child transportation safety by allowing for upper anchoring. Just like for the ISOFIX system, there must be special anchoring points in the vehicle for the Top Tether system, especially older cars do not have them. Additional anchoring points are usually integrated on the rear side of your car seat or located in the floor of the luggage compartment. Thanks to the Top Tether system, the seat is better secured, thereby reducing head load during frontal impacts.

princip uchycení sedačky systémem TOP TETHER  princip uchycení sedačky systémem TOP TETHER 

princip uchycení sedačky systémem TOP TETHER