Are sleep sacks safe for newborns to 6 month olds?

What the evidence says

Health Canada, the Canadian Paediatric Society, and HealthLink BC all say sleep sacks (also called wearable blankets) are a safe way to keep a baby warm during sleep, and many parents use them instead of a loose blanket. The key safety rule is fit: the sack needs to be the right size for your baby, because a too-big sack can let your baby slip down inside and risk overheating or suffocation, while a too-tight one can restrict hip and leg movement, which is especially risky if baby rolls onto their tummy. The American Academy of Pediatrics agrees, describing wearable blankets as preferable to loose blankets because they lower the chance of the fabric covering baby's head or causing entanglement.

Choose a thin, lightweight sack appropriate for room temperature so baby doesn't overheat, since overheating is itself a SIDS risk factor. One caution applies to swaddle-style sleep sacks that hold the arms snugly against the body: these should be stopped as soon as your baby shows signs of trying to roll, usually around 3 to 4 months, because a swaddled baby who rolls onto their tummy may not be able to move to a safer position. Non-swaddling sleep sacks that let baby move their arms and legs freely can be used for as long as you like, including through 6 months and beyond.

Also avoid weighted sleep sacks or blankets, which the AAP specifically advises against, and always place baby on their back on a firm, flat surface for every sleep, regardless of what sleepwear they have on.