At Car Seat Ninja, we're big believers in small details making a big difference — and nowhere is that more true than when it comes to your child’s harness fit.
As part of Child Safety Week, we’re spotlighting one of the most important (and often overlooked) safety checks: making sure your child’s harness is fitted correctly every single time you travel.
Why harness fit matters
Your car seat’s harness is designed to restrain your child in the event of a crash, spreading impact forces across the strongest parts of their body. But if it’s too loose, incorrectly positioned, or twisted, it can’t do its job properly — putting your child at risk of injury, even in minor collisions.
Key things to check every time:
1. A snug, secure fit
You should only be able to fit two fingers between the harness and your child’s collarbone. If the harness feels slack or if you can pinch the strap between your fingers, it’s too loose.
2. Harness height
For rear-facing seats, the harness should be positioned at or just below your child’s shoulders. In forward-facing seats, it should be at or just above the shoulders. The correct height helps keep your child properly supported during sudden stops or impacts.
3. Smooth and untwisted straps
The harness should lie flat and straight with no twists, which can concentrate force in one spot and cause injury in a crash.
4. Across the chest, not the tummy
Ensure the harness sits snugly against the chest and shoulders, but not too loose over the stomach (can be normal to have a small gap).
5. Avoid bulky clothing
Thick coats or padded clothing can compress in a crash, creating hidden slack in the harness. They can also cause overheating. Dress your child in thin, fitted layers and, if needed, add a blanket over the harness once they’re safely strapped in. Don’t forget that bulky hoods can also cause head lolling or misalignment.
Need a second opinion?
If you’re not 100% confident that your child’s harness is fitted correctly, we’re here to help! Feel free to send us a photo of your child in their seat via DM or email — our trained team can offer free, no-pressure advice.