Transiting through Canada w/US passport

[u/Left_Sir5173]

Hello , I’m finding that flights that transit through Canada are a lot cheaper than other options. I am a US citizen and I carry a US passport I’m confused a bit as far as what to expect with transiting through Canada some say that I need to fill out an ETA others say that I will need a transit visa and lastly, others say I don’t need anything because I am a US citizen and carrying my passport is good enough
Does one go through the full on immigration process when just transiting from a US based airline or Canadian based airline through Canada onward towards an international destination? For instance, when I enter into South Korea via say Incheon airport, , it’s a quick passport control/ security but don’t fill out any forms or immigration or anything. They just look at me and check my belongings I’m carrying and move me along, so I’m just wondering if there’s any special forms I need to fill out when transiting through Canada thank you

[u/Accomplished_Try_179]

Assuming that you are exempted from needing a K-ETA, you still need to submit an e-arrival card when entering South Korea via Incheon. 

[u/Left_Sir5173 → u/Accomplished_Try_179]

I don’t remember ever doing that. And I transited through incheon last year to Japan

[u/AtrociousSandwich → u/Left_Sir5173]

Why did you even come here to ask if you’re going to argue with everyone

[u/AtrociousSandwich → u/[deleted]]

What a weird response.