ISOFIX vs seatbelt car seats UK

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Does the law require ISOFIX?

No. GOV.UK requires an approved child seat that is fitted as the maker designed. ISOFIX is one method. A seatbelt route on an R129 seat is another. Prefer i-Size when buying new. Never put a rear-facing seat in front of an active frontal airbag. The finder names the category, not the click.

When does ISOFIX win?

When your car has the anchors in the seat you will actually use, and you want a fit that is hard to get wrong on a tired evening. A base you leave in the car can be the product. It still needs the handbook. A green indicator is not a reason to skip reading the manual. Compare listings that show a readable R129 label.

Compare ISOFIX bases at John Lewis*

When does a seatbelt-fitted seat win?

When a second car, a grandparent’s car, or a taxi has no ISOFIX. When you fly and the cabin wants a belt path. ISOFIX-only infant carriers often cannot use an aircraft lap belt. A belt-fitted option is flexibility, not a downgrade. See flying with a baby.

Should you buy two bases for two cars?

Only if you will actually click the carrier into both. Two bases can be cheaper than two whole travel systems. They are not a reason to skip a seat in the car you drive to hospital. Unknown-history second-hand bases follow the same skip as unknown seats. Check OPSS on a used base.