Originally Posted by turnips

Jetstar enforce the most heavily (at the gate) however it is still random. They also typically weigh and tag carry-on at check-in too. There is an option to buy additional carry-on allowance ahead of time (up to 10kg I think).

I have seen Qantas staff intermittently weighing bags at security queue in both Sydney T3 and Melbourne T1, however I'm unsure what (if any) action is taken if you're overweight. I've never experienced any enforcement from Qantas about carry-on and the sheer volume of bags you see people bringing onboard suggests it isn't common to be pulled up over it.

Originally Posted by JClasstraveller

JQ by far the strictest. Like Mwenenzi observed, they actively walk around looking for heavy-looking bags and have a mobile scale and credit card machine looking for revenue. I have seen VA staff weigh bags but rarely and to be fair, the ppl they picked on looked like they were carrying the kitchen sink with them. I’ve had QF ask once at SYD but I suspect staff had nothing else to do that day.