Are booster seats only ever held in place by the car seat belt?

[NDFB]

Are toddlers/children's booster seats only ever held in place by the car seat belt? So when there is no child in it you would still have to apply the seat belt to anchor it in place and stop it flying around in the car? Or are modern ones held in place with IsoFix connections? Otherwise, once the child is out, I imagine it is going to be a right pain to have to lean across in to the middle of the car heaving the seat belt in to place again.

@NDFB so there are car seats that go all the way up from birth or from toddler to around aged 4 that have isofix. I'm not sure if any of the older child ones have isofix or not but you don't have to rebuckle them when the child is out. The seat belt feeds through a kind of fitting thing which it stays into. Our boosters never move around the car when empty. But I do find leaning over my child to do up the buckle when she is in the car a pain.

We have three different boosters and they're all isofix

Are your dc not able to fasten their own seatbelts? My grandchildren can strap themselves in if I pull out enough of the strap to help them. No need for me to lean over.

Do you mean just the bottom bit boosters, or high back boosters? My DD (4) has just gone into her high back booster and while we use the seatbelt to secure her in as there are not separate belts, it is fixed in place with isofix.

We have the Maxi Cosi Kore Pro.

The majority of high back boosters and even a lot of backless boosters have isofix now. You don't have to use it, but it is useful to keep it stable and yes, prevent it from becoming a projectile in an accident.

You are supposed to secure a non-isofixed booster seat with the seatbelt even when empty, but hardly anybody does this.

Yes many are now isofix, it’s mainly for when empty and to just hold in place. But they are all only secured safety wise for child with seatbelt. You can opt to use without the isofix if using on space without isofix available.

As far as I'm aware, most harnesses don't work after a certain weight. Our high back booster is fixed in with isofix but it's the seat belt that holds the child in place

We have high-backed boosters which can be fixed in either with ISOFix or seat belt only. Regardless with a high-backed booster the child is held in via the car's seat belt, and not a separate harness.

Ours are Britax KidFix and come with various additional safety features, incluing a crotch strap that protects the pelvis and a pad on the seat belt that helps to spread the force of the belt in case of an accident. Also has extra side impact things (technical term).