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Best child car seats and high back boosters

Need a car seat for an older child? After five months of in-depth, parent-led testing, we reveal the seven best high back booster seats for 2021.

By Mumsnet HQ | Last updated Jun 15, 2021

child in high back booster seat Mumsnet Best

When your child has grown out of their toddler car seat and is almost ready for school, choosing a seat that will last them up to the age of 12 may well feel impossible.

After all, how can you pick a car seat for your pre-schooler that will also see them right through to secondary school?

We've done the research and testing and narrowed down our 2021 picks to help you make that all-important choice.

How we chose the products to test

We commissioned Alison Williams to research the best child car seats on the market.

With two grown-up children, she has experienced almost all the stages of parenthood and has previously written articles on a wide range of parenting subjects, including reviews of baby car seats, toddler car seats, breast pumps and maternity pillows for Mumsnet.

Alison spent approximately 30 hours researching the UK's top seats. This included looking at crash test results and price points, scouring the Mumsnet forums to find out which seats parents were raving about, researching old favourites as well as those that were new to market and, finally, looking at which innovative designs were really making parents’ life easier.

She also checked out reliable consumer sites like Which, Honest John and Wirecutter, and studied reviews on Amazon, Feefo, Trustpilot, Uber Kids and Halfords.

Most importantly, she researched the latest safety innovations and regulations to make sure that every seat we tested and recommended reached those standards. She spoke to CO Jan James of Good Egg Car Safety and Margaret Bolt, founder of Rear-Facing Toddlers, to make sure that she thoroughly understood the latest regulations and safety advice when it came to recommending car seats.

How real-life comparative testing makes Mumsnet Reviews unique

Following the research stage, Alison then came up with a longlist of 25 car seats that were then narrowed down to a shortlist of 12 for testing with a family over a period of five months.

To do this, Alison teamed up with Jemma, a mum of three, whose five-year-old daughter used the car seats in the family’s Citroën Grand C4 Picasso. The seats were also occasionally used with her four- and seven-year-old nieces.

When testing products in a single category, we think it’s really important to work with one tester to ensure consistency in our results and to make comparison easier. We also think it’s fairer to put all the seats through the same rigorous testing process using the same children and the same day-to-day routine.

High back booster seats are often very similar so, on paper, there may not be much difference between them. Working with one tester means that those small differences – the thoughtful details that make life that little bit easier for parents and, equally, the little niggles and irritations that negatively affect day-to-day use – can be seen and experienced much more clearly.

Once testing had finished, the seats were then scored on the following criteria: safety and stability, assembly, day-to-day use, cleanliness, aesthetics and value for money. The five highest-performing products that offered the best value for most parents were awarded a Mumsnet Best badge and two others were also chosen as recommended buys.

And the results are in. Here are the seven best high back booster seats for 2021.

1. Best overall child car seat: Maxi-Cosi Kore i-Size

maxi cosi kore i-size car seat

Packed full of safety features, including Side Protection System Plus (SPS), the Maxi-Cosi Kore i-Size is a reliable and comfortable seat for a growing child.

As well as boasting top-notch safety credentials, the Kore's sleek design means that it should continue to appeal to your child as they get older. It looks and feels more expensive than it is, and it’s also easy to clean – crucial in a seat that will last for multiple years.

Although we found the ISOFIX connectors stiff to use at first, the Kore is both simple to use and to install. Conforming to the new R129 regulations, the only other seat we tested to do this was the much more expensive BeSafe iZi Flex Fix i-Size.

Maxi-Cosi's lifetime warranty is also something none of the other manufactuers offer – and is definitely something to bear in mind when considering the car seat's longevity.

While we also tested and liked the Maxi-Cosi Kore Pro i-Size, an updated version of the Kore i-Size which has additional features and premium bamboo fabrics, we felt the value and the simplicity of the Kore (often a benefit when it comes to car seats!) was something not to be ignored.

Great for parents who

  • Need a seat that will, quite literally, go the distance
  • Want a seat that's convenient to use as well as stylish


  • Conforms to the R129 car seat safety regulations and fits any car with ISOFIX
  • Quick and easy to fit – it took our tester a matter of minutes
  • Simple headrest adjustment
  • Width of the seat increases with the height of headrest
  • Open design makes it easy for your child to get in and out
  • Lifetime warranty covers all manufacturing defects


  • ISOFIX connectors feel a little stiff at first
  • Only available in plain colours

Key specs

  • Age range: Approximately three-and-a-half to 12 years; 100 to 150cm
  • Safety credentials: Complies with ECE R129/03; Side Protection System Plus (SPS)
  • Fixing system: Three-point seatbelt and ISOFIX or seatbelt only
  • Dimensions: 51 × 44 × 76cm
  • Weight: 5.9kg
  • Guarantee: Lifetime

Read the full review

2. Best value child car seat: Cozy N Safe Augusta EZFix

cozy n safe augusta car seat

Being a parent is expensive, so if you’re looking for a safe, comfortable and good-looking seat that won’t break the bank, the new Cozy N Safe Augusta EZFix could well be the answer.

The lowest priced seat of all on test, the Augusta EZFix, like its competitors, can be installed using ISOFIX. It also features armrests, deep seat padding and reversible covers to keep your small passenger happy and your car completely stain-free.

We do wish the headrest was generally easier to adjust, but this is a minor downside to an otherwise high-performing, great value seat. At less than £100, you can't really go wrong.

Great for parents who

  • Need a lightweight car seat to switch between cars
  • Are on a tight budget


  • Very simple to install
  • Lightweight at less than 5kg
  • Adjustable headrest
  • Covers very easy to remove
  • Great value for money


  • Basic, no-frills design
  • Headrest can be tricky to alter
  • Covers not machine-washable

Key specs

  • Age range: 15 to 36kg; Group 2/3
  • Safety credentials: R44/04 compliant
  • Fixing system: Seatbelt and ISOFIX or three-point seatbelt only
  • Dimensions: 68 × 44 × 46cm
  • Weight: 4.9kg
  • Guarantee: 12-month warranty

Read the full review

3. Best versatile child car seat: BeSafe iZi Flex Fix i-Size

besafe izi flex fix i-size car seat

“The BeSafe iZi Flex Fix is very good, although it's also very expensive.” - Mumsnet user

Trying to squeeze three car seats into the back of the car? The slim design of the BeSafe iZi Flex Fix i-Size is ideal for families who need a bit more flexibility day-to-day.

We love the fact that the manufacturer has really considered what parents need when designing this seat. With children required by law to use a car seat or booster until they are 12 years old or 135cm (whichever comes first), it can often be tricky to find a configuration of seats to fit a packed family car. The versatility of the iZi Flex Fix means this is much easier to accomplish.

But it's not just the seat's versatility that impressed us. Like the Maxi-Cosi Kore i-Size, the iZi Flex Fix conforms to the latest R129 regulations, but, unlike our overall winner, it's also equipped with three (yes, three!) layers of Side Impact Protection for maximum safety and comfort.

Yes, it may be pricey for parents on a tighter budget, but we think the BeSafe iZi Flex Fix i-Size is nevertheless a great choice for busy families.

Great for parents who

  • Have more than one child under 12 years of age
  • Regularly go on long car journeys


  • Conforms to R129 safety regulations
  • Has a recline function, which is great for longer journeys
  • Boasts lots of safety features, including PAD+ for additional chin and chest protection
  • Slim design but still with plenty of space for a growing child
  • Adapt so that parents can fit three car seats in a row


  • The covers are a bit tricky to put back on after washing
  • Can be pricey (so do shop around)

Key specs

  • Age range: Three-and-a-half to 12 years; 100 to 150cm
  • Safety credentials: Conforms to R129; ADAC rated 'Good' (1.9); Side Impact Protection Plus (SIP+); PAD+
  • Fixing system: Seatbelt and ISOFIX or three-point seatbelt only
  • Dimensions: 42 × 52 × 64cm (in lowest position and including SIP bumpers); width without SIP bumpers: 44cm; seat height in highest position: 82cm
  • Weight: 7kg
  • Guarantee: Two years

Read the full review

4. Best child car seat for ease of use: Britax Römer Kidfix III M

britax romer kidfix car seat

“We have two Kidfix seats. They're fab and both kids like them.” - Mumsnet user

A breeze to operate in an ISOFIX-ready or seatbelt-only car, the Britax Römer Kidfix III M is our top pick for ease of use.

Everything about this seat is simple, whether that’s installing the seat in your car, adjusting the ergonomic headrest or removing, washing and replacing the covers. It’s really comfortable too, which is crucial considering how long you'd need the seat to last.

While it is one of the bulkiest seats we tested and too heavy to lift between cars, if you’re looking for a seat that ticks all the boxes when it comes to safety, style and practicality, then the Britax Romer Kidfix II M is an excellent choice.

Key features also include a large seating area, a V-shaped backrest that grows with your child, and SecureGuard and Side Impact Cushion Technology (SICT) for extra protection in the event of a collision.

Great for parents who

  • Need a seat that’s quick and easy
  • Have tall children who need a bit more growing room


  • Installation takes approximately five minutes
  • Headrest simple to adjust for different heights
  • Covers easy to remove, wash and replace
  • Longer seating area means added comfort for even the tallest of children
  • V-shaped backrest grows with your child
  • Excellent safety credentials


  • May be tricky for a child to strap themselves in if there are three seats installed in a row
  • Bulky and heavy

Key specs

  • Age range: 15 to 36kg; Group 2/3
  • Safety credentials: Conforms to R44/04; ADAC 'Good' (1.7); OAMTC 'Good'; Stiftung Warentest 2019 'Best in Test'; SecureGuard; Advanced Side Impact Protection
  • Fixing system: Three-point seatbelt and ISOFIX or three-point seatbelt only
  • Dimensions: 67 to 45 × 54 × 43cm
  • Weight: 7.5 kg
  • Guarantee: Two years

Read the full review

5. Best lightweight child car seat: Apramo Ostara Fix

apramo ostara fix car seat

If you’re a family that likes to travel, or if you need to transfer a seat from car to car, then the lightweight Apramo Ostara Fix may be right up your street.

Heavily padded around the head, sides and hips to keep your child secure and comfy at all times, the Ostara Fix also has Superior Side Impact Protection, providing extra cushioning in the event of a side collision.

At just 5.5kg, it gives you the option of taking your own car seat with you when you travel, and is ideal if you plan to use your seat in multiple cars – it's light enough to make installation that much less of a chore.

The only downside is the headrest which was tricky to adjust despite boasting seven different settings, however we love how easy the seat is to clean – and its price tag is a bit of a boon too.

Great for parents who

  • Travel frequently
  • Often need to switch car seats between cars


  • Lightweight – good for on the move
  • Easy and quick to install
  • Simple design
  • Seat covers easy to remove


  • Headrest difficult to adjust
  • Fabric could be irritating to sensitive skin

Key specs

  • Age range: 15 to 36kg; Group 2/3
  • Safety credentials: Conforms to ECE R44/04; Superior Side Impact Protection (SSIP)
  • Fixing system: Three-point seatbelt and ISOFIX or seatbelt only
  • Dimensions: 73 × 48.5 × 48cm
  • Weight: 5.5kg

Read the full review

6. Recommended buy: Diono Everett NXT

diono everett car seat

The Diono Everett is the ideal car seat for travelling. At just 4kg, it's lighter than both the Cozy N Safe Augusta EZFix and the Apramo Ostara Fix, but didn't perform as well during testing, particularly when it came to adjustments and overall stability.

It is great value though, offering an ISOFIX option despite its budget-friendly price tag, with lots of padding designed for maximum comfort and covers that are easy to remove, machine-wash and refit.

Our tester also found it easy to install.

Great for parents who

  • Need a light seat for travelling or moving from car to car
  • Are on a budget


  • Lightweight so great for travelling
  • Cushioned headrest with Side Impact Protection
  • Memory foam support cushions for extra comfort
  • Great price


  • Headrest difficult to adjust
  • Our tester felt there was a slight wobble when using ISOFIX (without a child in the seat)

Key specs

  • Age range: 15 to 36kg; Group 2/3
  • Safety credentials: R44/04 compliant
  • Fixing system: Belted and ISOFIX or three-point seatbelt only
  • Dimensions: 72 × 46 × 41cm
  • Weight: 4kg
  • Guarantee: 12 months

7. Recommended buy: Maxi-Cosi Kore Pro i-Size

maxi cosi kore pro i-size car seat

Maxi-Cosi's Kore Pro i-Size has all the safety and comfort of the Maxi-Cosi Kore, but boasts additional features, including a ClickAssist light.

This is an innovative addition that our tester and her daughter really enjoyed. The light illuminates the seatbelt socket for 30 seconds once a child is in the seat, which helps them to buckle themselves in, even in the dark.

In contrast to the regular Kore, the Kore Pro's covers are made from premium bamboo fabrics to keep a child cool in warmer weather.

Great for parents who

  • Feel they would benefit from additional features
  • Have a child that craves independence

Pros ·

  • Conforms to R129
  • ClickAssist light for easy buckling in
  • Bamboo fabric covers
  • Simple installation
  • Lifetime warranty covers all manufacturing defects


  • ISOFIX connectors feel a little stiff at first
  • More expensive than the Maxi-Cosi Kore i-Size – our tester thought the ClickAssist light wasn't worth the extra cost

Key specs

  • Age range: 100 to 150cm
  • Safety credentials: Complies with ECE R129/03; Side Protection System Plus (SPS)
  • Fixing system: Seatbelt and ISOFIX or three-point seatbelt only
  • Dimensions: 51 × 44 × 76cm
  • Weight: 6kg
  • Guarantee: Lifetime

What are the different types of child car seats?

UK law states that all children need to be in a car seat up to the age of 12 or 135cm (whichever comes first). When buying a seat at this stage, ideally you'll want it to last until your child no longer needs one.

Child car seats fall into five groups:

1. Group 1/2/3 (R44/04) – from 9 to 36kg, or around nine months to age 12 (or 135cm)

2. Group 2 (R44/04) – suitable from 15kg to 25kg, or approximately four to six years of age

3. Group 2/3 (R44/04) – from approximately four years up to age 12 or 135cm (15 to 36kg)

4. Group 3 (R44/04) – can be used with children who weigh 22kg to 36 kg and are 125cm or taller

5. i-Size (R129) – conforming to the R129 regulation, i-Size car seats for this age group can be used from 100 to 135cm (or from 135cm to 150cm in specific cars)

What is a high back booster seat?

A high back booster is a child car seat used from approximately age three to 12. It has sides (usually well-padded) and a headrest, and it will provide routing for the shoulder and lap part of the vehicle's seatbelt.

Depending on the specific seat and the car it's fitted in, it can often be used in combination with ISOFIX fixings.

What is a backless booster seat and is it safe?

A backless booster seat is a seat cushion for children, which can be routed into the car using only the lap part of the seatbelt.

Legislation around high back booster seats and booster cushions changed in March 2017. An amendment to R44/04 means that new-to-market backless booster seats approved after this date can only be used with children weighing more than 22kg and who are taller than 125cm.

If a booster cushion was approved before this amendment, the approval relates to Group 2/3 (15 to 36kg) seats. As such, if the label on the booster cushion has a stated weight of 15kg to 36kg, it is still legal to use.

However, as Jan James from Good Egg Car Safety points out, this doesn’t mean it’s the safest option for a younger child. Booster cushions are unable to provide the side impact protection that a high back booster can. As such, it is recommend that parents use a high back booster instead.

What is i-Size?

i-Size car seats meet the new R129 European car seat safety standards that came into force in July 2013, which aims to increase the safety performance of all car seats on the market.

R129 regulations are currently running in parallel with R44 so you can buy car seats that adhere to either guidelines. At some point, R44 car seats will be phased out of the shops – but it's unclear exactly when this will happen.

What are the differences between R44 and R129?


  • Classification based on weight
  • Rear and front impact testing
  • Can be fitted using seat belt or ISOFIX points
  • Seat must be rear-facing until your child weighs 9kg


  • Classification is based on height
  • Rear, front and side-impact testing
  • Seat is attached using ISOFIX points
  • Seat must be rear-facing until your child is older than 15 months

How much should I spend on a car seat?

Prices vary considerably and it is worth looking into exactly what higher-priced seats are offering before spending any money as the most expensive seats aren’t necessarily the best.

Safety is the most important thing and all car seats must conform to R44 or R129 regulations. Bigger brands often conduct their own safety testing too.

So, if you’re on a tight budget, do keep safety in mind as your first priority and make sure you always check independent reviews before buying.

Can you use secondhand car seats?

A car seat's main job is to protect your child and, for that purpose, it tends to be a single-use item. You can use a car seat until you have an accident, at which point it must be thrown away and replaced.

While secondhand seats aren't necessarily unsafe, if you buy a seat from someone you don't know you have no real way of knowing the seat's history. This may not be the case if it's been passed down from a relative or a friend, but even if the seat looks fine, it could still have suffered invisible damage that has made it weak or unsafe.

As such, experts from Good Egg Car Safety recommend never buying a secondhand car seat.

How we tested our selection of child car seats

Our tester, Jemma, used the child car seats we tested exactly as any mum would. They were tested right from the very start – from the unpacking and assembly of the seat when it arrived to installing it into the car.

Each seat was used on the daily school run and on longer trips of up to an hour. They were also switched between cars and different-aged children before being scored on other practicalities like stain removal, washing and getting pesky covers off and back on again.

Here's what we looked at for each of the six key testing criteria.

Safety, stability and comfort

  • Crash test results
  • How easy was the seat to install – was there any room for error?
  • Additional safety features
  • Materials – are they durable and robust?
  • How comfortable was the child in the seat?
  • Was there anything about the seat that could distract the parent while driving?


  • Were clear instructions provided?
  • Was everything needed for set-up included in the box?
  • Did the seat need more than one person to install it?
  • Was the seat easy to install overall?
  • Were there a website and a customer service helpline if you got stuck?

Day-to-day use

  • Could the child get in and out of the seat quickly and safely?
  • For longevity – could the seat grow with a child?
  • Was it easy to adjust the seat if you needed to use it with a child of different ages?
  • Was it easy to strap your child in the seat when you were in a rush? Could they do it themselves?

Aesthetics and cleanliness

  • Was the seat easy to clean? We spilled milk and juice on each seat to see how it fared after cleaning
  • Were the covers removable for washing, and were they easy to put back on afterwards?
  • How does the seat look overall? Is the fabric good quality? Would the seat still appeal to your child as they grow?

Value for money

  • Does the seat offer good value for money?
  • Does the price seem reasonable, particularly given the length of time it will be used?

Why you should trust us

All Mumsnet product reviews are written by real parents. We work hard to provide honest and independent advice you can trust – brands can’t pay to be featured in our articles or win a Mumsnet Best award.

We spend hours researching, speaking to parents, analysing data and listening to experts before we test out the products on our shortlist.

Transparency is really important to us and that's why we're always upfront about how we tested the products we recommend. We won't always recommend the cheapest products or the ones with the most extra features. We write about products that we feel offer the best value to most parents – the ones we'd recommend to our own friends and family.

We do sometimes earn revenue through affiliate (click-to-buy) links in our articles. This helps us fund more helpful and independent review pieces like this one. However, we never allow this to influence our coverage.

There's no incentive for us to be lazy with our research or in our testing process. There's no reason for us to respond to pressure from retailers or brands trying to promote new products. It's actually quite the opposite and we think it's a good system, one that keeps us focused on making parents lives' easier.

All prices on this page correct at time of writing.