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CERTAIN CONTENT THAT APPEARS ON THIS SITE COMES FROM AMAZON. THIS CONTENT IS PROVIDED ‘AS IS’ AND IS SUBJECT TO CHANGE OR REMOVAL AT ANY TIME.
Price on Amazon.com as of 2026-11-01 12:11 UTC, and subject to change.
An all-in-one car seat with 4 modes: rear-facing harness 5 to 40 lb, 19 to 40 in; forward-facing harness 30 to 65 lb, 34.4 to 49 in; belt-positioning booster (high-back) 40 to 100 lb, 43.4 to 52 in; backless booster 40 to 100 lb, 43.4 to 57 in.
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CERTAIN CONTENT THAT APPEARS ON THIS SITE COMES FROM AMAZON. THIS CONTENT IS PROVIDED ‘AS IS’ AND IS SUBJECT TO CHANGE OR REMOVAL AT ANY TIME.
The Maxi-Cosi Kani 4-in-1 is an all-in-one seat with four modes: rear-facing harness for 5 to 40 lb and 19 to 40 in., forward-facing harness for 30 to 65 lb and 34.4 to 49 in., then high-back and backless booster for 40 to 100 lb. The manual says not to use it more than 10 years after manufacture.
The Kani suits a family that wants one seat from the hospital ride to a backless booster, including a backless mode that the manual allows to 57 in. The trade-off is weight, at 23.2 lb by Maxi-Cosi's figure. Compared with the Pria family, it adds the backless mode, 5 recline positions instead of 3 and a 10-position headrest instead of 5, but its lower anchors stop at a child weight of 45 lb where the Pria manual allows 50 lb.
A research summary of Maxi-Cosi’s published specifications and manual, read . Not a hands-on test or a crash-safety rating.
This seat covers 4 stages, and a child has to meet every limit of the stage they are in. Maxi-Cosi gives it a 10-year life from the date of manufacture, so check the date label before using a hand-me-down.
| Mode | Child weight | Child height | Minimum age | Conditions |
|---|---|---|---|---|
| Rear-facing harness | 5 to 40 lb | 19 to 40 in | Not published | — |
| Forward-facing harness | 30 to 65 lb | 34.4 to 49 in | Not published | — |
| Belt-positioning booster (high-back) | 40 to 100 lb | 43.4 to 52 in | Not published | — |
| Backless booster | 40 to 100 lb | 43.4 to 57 in | Not published | — |
A child must meet every limit for the mode they use. The labels on your seat and its manual are the final word.
Every install is a fit between one seat and one vehicle. Read both manuals, and use a free inspection station if anything is unclear.
Maxi-Cosi does not publish a width for this seat, so measure your back seat and compare it with the seat in a store before buying. It weighs 23.2 lb, which matters if you will move it between cars or carry it through an airport.
Caspian Caviar.
The manual gives two methods in each direction, the vehicle belt or the lower anchor belt, and says never to use both at once. Rear-facing, the tether stays stored and the seat must touch the seat in front or be as close as possible. Forward-facing, you put the seat in Position 1 and must always use the tether when anchors are available. The lower anchors are not for a child over 45 lb; from there the vehicle belt is required. In either direction the seat should not move more than 1 in. side to side at the belt path.
Source: Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF)
The Kani has 5 positions. Rear-facing uses Positions 5 to 2, and Position 1 is never allowed rear-facing. For a child of 5 to 30 lb and 19 to 34.3 in., the bottom level line on the seat must be parallel with the ground. For a child of 30 to 40 lb and 34.4 to 40 in. who can sit up unassisted, the top level line applies instead. If you cannot reach the line, the manual permits tightly rolled towels or foam pool noodles under the front of the seat. Forward-facing and both booster modes use Position 1, fully upright.
Source: Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF)
For booster use you store the harness system and remove the head pillow, body pillow and harness covers. With the back on, the booster fits 40 to 100 lb and 43.4 to 52 in. To go backless, you squeeze two release levers under the pad and pull the backless booster out of the main seat. That mode runs to 57 in. A shoulder belt positioning clip is used in backless mode only, and only if needed. With the back on, the tops of the child's ears must not be above the top of the booster headrest; backless, they must not be above the top of the vehicle seat back or headrest. The lap belt alone is never enough.
Source: Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF)
The seat pad and accessories go in the machine separately, in cold water on a gentle cycle, with the harness covers closed so the fastening strips are not exposed. No bleach. Tumble dry separately for 10 to 12 minutes on low heat and remove immediately. The harness straps, buckle and shell are spot cleaned with warm sudsy water and a damp cloth, and the buckle must not be submerged. The manual warns never to pull the harness strap fully out of the seat, because it cannot be rethreaded. The two cup holders are top-rack dishwasher safe.
Source: Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF)
No campaign in the current NHTSA child-restraint data names this model family, and I have not run a separate review for it. Check your seat’s model number and date of manufacture before use.
The manual says the child must stay rear-facing until reaching 40 lb or 40 in., or failing the rear-facing fit requirements, including keeping the top of the head at least 1 in. below the top of the headrest. Forward-facing harness use starts at 30 lb and 34.4 in. and runs to 65 lb and 49 in.
Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF) (opens in a new tab)
Yes, but only for a child weighing up to 45 lb. Above 45 lb the manual requires the vehicle belt, and the tether must always be attached forward-facing with the harness when anchors are available.
Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF) (opens in a new tab)
The manual says it is certified for aircraft use with the internal harness. It is not certified as a booster because aircraft seats have no shoulder belts. Forward-facing on a plane, you follow the vehicle belt steps but skip the tether steps, and you must store the lower anchor belt and tether.
Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF) (opens in a new tab)
The manual gives 43.4 to 52 in. for the backed booster and 43.4 to 57 in. for the backless booster, both for 40 to 100 lb. In backed mode the child also outgrows it once the tops of the ears are above the top of the headrest.
Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF) (opens in a new tab)
Maxi-Cosi's product page says its slim design fits 3 across most vehicle back seats, but the page gives no width measurement. I would measure the back seat and check the seats it will sit next to before relying on that claim.
Maxi-Cosi Kani 4-in-1 Convertible Car Seat product page (opens in a new tab)
Yes. The manual says not to use the magnetic chest clip with a child who has an implanted electronic medical device, and Dorel will send a non-magnetic replacement clip free of charge if the parent or child has one.
Maxi-Cosi Kani 4-in-1 Convertible Car Seat user guide (PDF) (opens in a new tab)
Answers refer to the model and manual version on this page. Check the instructions supplied with your seat.
| Model | Top child weight | Seat weight | Width | Usable life |
|---|---|---|---|---|
| Kani 4-in-1 Convertible Car Seat (this seat) | 100 lb | 23.2 lb | — | 10 years |
| Sela All-in-One Convertible Car Seat | 100 lb | 27.25 lb | — | 10 years |
| Pria Max+ All-in-One Convertible Car Seat | 100 lb | 16.5 lb | — | 10 years |
| Pria Max All-in-One Convertible Car Seat | 100 lb | 16.8 lb | — | 10 years |
| Pria All-in-One Convertible Car Seat | 100 lb | 16.5 lb | — | 10 years |
| Petra All-in-One Convertible Car Seat | 100 lb | 14.75 lb | — | 10 years |
| Romi 2-in-1 Convertible Car Seat | 50 lb | 9.2 lb | — | 10 years |
Other all-in-one seats whose published weight and height limits overlap the Kani 4-in-1 Convertible Car Seat.
| Mode | Weight | Height |
|---|---|---|
| Rear-facing harness | 5–40 lb | 19–40 in |
| Forward-facing harness | 30–65 lb | 34.4–49 in |
| Belt-positioning booster (high-back) | 40–100 lb | 43.4–52 in |
$229.99Sea Shadow · Amazon price as of 2026-11-01 12:11 UTC, subject to change
| Mode | Weight | Height |
|---|---|---|
| Rear-facing harness | 5–40 lb | 19–40 in |
| Forward-facing harness | 30–65 lb | 34.4–49 in |
| Belt-positioning booster (high-back) | 40–100 lb | 43.4–52 in |
$269.99Sea Shadow · Amazon price as of 2026-11-01 12:11 UTC, subject to change
| Mode | Weight | Height |
|---|---|---|
| Rear-facing harness | 5–40 lb | 19–40 in |
| Forward-facing harness | 30–65 lb | 34.4–49 in |
| Belt-positioning booster (high-back) | 40–100 lb | 43.4–52 in |
$329.99Esgargot · Amazon price as of 2026-11-01 12:11 UTC, subject to change
| Mode | Weight | Height |
|---|---|---|
| Rear-facing harness | 5–40 lb | 19–40 in |
| Forward-facing harness | 30–65 lb | 34.4–49 in |
| Belt-positioning booster (high-back) | 40–100 lb | 43.4–52 in |
$329.99Sea Shadow · Amazon price as of 2026-11-01 12:11 UTC, subject to change
