Years ago, I stopped using snap hook leashes. If you don't know what a snap hook is, it's the most common hook for dog leashes.
I stopped using them because they can easily be jostled loose and off. Especially when using coats. They're not secure, literally being held on by a spring with no other positive lock. After this happened a few times, I switched to locking carabiners.
Ruffwear was what I used first, but their carabiners don't swivel, nor do they auto lock. So through the course of a walk, the leash would twist and curl. I actually modified them with some swivels I found later, but that added weight.
Then I discovered Tuff Mutt on Amazon, and gave them a shot. When I adopted Leeloo, I got a second one because I loved it so much.
I've used these for years. They're easy to use, strong, secure, durable, and light.
They're on sale for Prime Day.
https://www.amazon.com/dp/B078H62QZK/
(this is not a paid ad or anything, I just think they're really good and the price is really good)