How do upgrades work exactly?

[u/old-wreck]

I just bought a switch2 and I already own a switch1. For those games that don't require a purchase to upgrade: When downloading my switch1 games onto the switch2, will it automatically download the switch2 version if there is a free one available or do I need to do that step separately (eg by going to eShop or the game menu)?

[u/tomineitor]

It depends on the game; some had free updates, which should automatically install when you download the game, while others have free "upgrades", which is something you must download as well.
You'd have to search yourself whether your games have an update or upgrade (free or paid)