Safety 1st Ever Slim car seat

The best car seat is the one that fits your child, vehicle, budget, and lifestyle and has the features important to you. The safest car seat is the one you can install correctly and use properly on every ride! Let us know in the comment section what questions you have about this Safety 1st EverSlim car seat review.

Safety 1st EverSlim Car Seat Review (USA)

This is one of the newest narrow seats on the market at 17″ wide. It’s touted as an all-in-one seat, but with the backless booster limit currently at 52,” you will need another backless booster once this seat is outgrown. But since backless boosters are inexpensive, this won’t be a dealbreaker for most people. This seat will still last many kids until 7 or 8 years old.


A 4-in-1 car seat that can be used rear-facing, forward-facing, in high-back booster mode, and in backless booster mode.


From birth (for average/large newborns) or after the infant seat is outgrown


Our recommendation: Birth until the seat is outgrown (average 6/7 years old)

What you need to know before you go.

Safety 1st Ever Slim

Rear-Facing Seat Stats

  • height limit: 19-40″
  • weight limit: 5-40 pounds
  • head height rules: head must be at least 1″ below the top of the headrest

Forward-Facing Seat Stats

  • height limit: 29-49″
  • weight limit: 22-65 pounds
  • head height rules: ears must be below the top of the headrest

Booster Stats

  • height limit: 43-52″
  • weight limit: 40-100 pounds
  • head height rules: ears must be below the top of the headrest

Other Seat Stats

  • width of seat: 17”
  • weight of seat: 30 pounds
  • crash replacement policy: Replace after moderate or severe crash
  • expiration limits: 10 years
  • harness: no-rethread
  • lock-off: no
Safety 1st Ever Slim features
Safety 1st Ever Slim on car

✅ Seat is good for you if:

✅ You need to fit 3 across in your vehicle.
Safety 1st EverSlim Review

Since this seat is only 17″ wide, it can fit 3 across in some vehicles. It doesn’t have any ease of installation features, so it’s not as easy to install 3 car seats with this seat, but it is doable. Above, you can see 3 across in a 2012 Toyota Camry with a Safety 1st EverSlim, Safety 1st SlimRide, and Evenflo Litemax. You may need to try different configurations in order to fit seats 3 across in your vehicle. See our blog here for more narrow car seat options and our YouTube video.

✅ You want to use a convertible seat from birth.
convertible car seat

This seat’s lowest harness height is 6.5″, so it will fit average or larger newborns from birth if you want to skip the infant seat. This seat has a good recline setting for infants, so it works well in that regard too, but it does take up a lot of space front to back at the required recline. The harness pads are very bulky and will need to be removed for a newborn. If you are expecting a premature or low birth weight baby, we would recommend a different seat like one of these.

✅ Your child is below the 50th percentile for height.

The highest harness height is only 16.5″ tall, while many other seats in this category have harness heights that are 17+.” Harness height is one of the indicators of how long a seat will last. However, if you have a child who is below the 50th percentile in height, this harness height will likely be adequate to get them to a safe booster age. The highest belt guide position on this seat is only 18.5″, so it lasts about two years longer than the harness mode. Even a lower percentile child will need another backless booster once this seat is outgrown.

✅ You have a child who likes to unbuckle the chest clip.
car seat chest clip

This seat has one of the hardest chest clips around for a child to unbuckle. It’s magnetic, and you have to squeeze two buttons while also moving half of the chest clip away from the other half, which is very difficult for most toddlers to manage. If you have a child who has escaped from multiple car seats already, try this one.

✅ You need a rear-facing seat that is compact from front to back.
rear-facing car seat

The Safety 1st EverSlim has 4 recline options for rear-facing. For kids who cannot sit unassisted, you must recline the seat until the red line on the side of the seat is parallel to the ground. In this more reclined position, the seat does take up a fair amount of space. But once the child can sit unassisted, you can use it as upright as you can get it in your vehicle. In the vehicle we tried this seat in, having the seat as upright as possible gave about 5″ of extra space to the front passenger versus how they would have had to sit when the seat was in the most reclined position.

🚩 Use Caution If:

🚩 You want only to buy one seat ever.

This seat currently has a 52″ standing height limit for the backless booster mode. We’ve been told that the manufacturer is working on raising that limit to 57.” But in the meantime, that means that a child would need another backless booster once this seat is outgrown. We’ve found that only around 50% of kids can pass the 5-Step Test at 57″, so far fewer would pass at 52″, likely 0% of kids. While this seat will still last many years, purchasing another booster will be necessary.

🚩You have a larger percentile child.

The highest harness height is only 16.5″ tall, so if you have a child with a long torso, this is probably not the best seat for you. This is relevant because you need the harness to come from even with or just above their shoulders when forward-facing. Many other seats in this category have harness heights that are 17+ inches. The highest belt guide position on this seat is only 18.5″, so it’s not long-lasting in the high-back booster mode either. But it does have a backless booster mode that can be used until the child is 52.”

⭐️ Stand Out Features:

⭐ Magnetic Chest Clip
Magnetic Chest Clip

This chest clip is easy enough for us adults to buckle. But for a kid, they will struggle to undo it. This is a great thing for toddlers who like to unbuckle. It may be challenging for caregivers who have limited use of their hands to unbuckle this chest clip, however.

⭐️ Harness Storage
Harness Storage

For high-back booster mode, the harness stores on the seat, so you only have to worry about storing the insert and harness pads. The padding is optional anyways, so if you lose that, the seat will still be usable in harness mode in the future. The harness storage is a little unusual, but the manual has instructions on how to do it. We like to see harness storage on seats that convert to boosters to reduce the chance of caregivers losing integral pieces.

⚠️ Quirks to be Aware Of:

⚠️ 52″ Limit for Backless Booster Mode

While the manufacturer has mentioned raising the limit to 57″, the manuals have not been updated to reflect this higher limit. So at this time, caregivers must stop using the backless booster mode once their child reaches 52″. The backless booster mode gave a good seat belt fit for both of the kids that we tried in it. You will need to purchase another booster, as a child who is 52 inches will not pass the 5-Step Test and be ready to just use the adult seat belt.

✈️ Airplane Use

The Safety 1st EverSlim is an FAA-approved car seat. At 30 pounds, it is fairly heavy, so there are better options than this one, and you can find some of those here. If traveling internationally, you will need a locking clip in order to do a seat belt installation since this seat does not have a seat belt lock-off. Contact the car seat manufacturer for a free locking clip. We have a video here of how to use a locking clip.

For help with all things airplane travel and car seats, check out our Wheels Up Course and private Facebook group.

SITS Bottom Line

If you have a child who is below the 50th percentile for both height and weight and you are looking for an all-in-one seat, this may be the seat for you! It’s narrow so that it may work in some 3 across situations. Remember that your child will need another backless booster in the future since this one currently has a 52″ limit.

Other Versions of this seat:

Compare Car Seats

Looking to compare car seats and narrow down the best car seat for your family? The Convertible Car Seat Buying Kit walks you through our 7Cs of selection, then on to an interactive quiz, and finally, a recommended car seat list is generated just for you! If you are overwhelmed and sick of spending hours researching and reading car seat reviews like this one, the Buying Kit will guide you to Safe in the Seat’s recommended car seats for you in under 30 minutes!

We check every day for our recommended car seats on sale, and we have all the deals here for you. Shopping in Canada? Find today’s seat sales in Canada here.

What About Seats We Don’t Recommend?

Just like anyone, we have preferences! This goes for car seats, too. If we don’t recommend a car seat, it’s not because it’s unsafe for your little one. All car seats are safe if they’re installed and used properly, are not expired or damaged, and when they’re made and sold by a reputable manufacturer and/or retailer. Click here for our full list of car seats that we do not recommend.

A note about crash-tests

How does the Safety 1st EverSlim perform in crash tests? 

Well, that’s a great question. We know it passes the strict federally required testing for all car seats sold in the United States. But we don’t know exactly how it performs. That data isn’t released by any official sources in the US — not by car seat manufacturers, not by government agencies like NHTSA, not anywhere! 

There are a few third-party websites that claim to offer objective crash test data that compares car seats. But we at Safe in the Seat ignore that data for a few big reasons. First of all, third-party car seat crash tests don’t actually give us meaningful data! Car seat manufacturers crash-test their products hundreds, even upwards of a thousand times. They crash test the finished product in every single installation configuration using every applicable-sized crash test dummy, not to mention a whole lot of testing at each stage of the development process too. So one or two crash tests completed by another organization just can’t give the same level of information! One or two crash tests aren’t going to represent the overall average performance of any car seat across its lifespan.

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