The Genshin Impact 5.4 codes are just another way you can add a few extra Primogems to your stash in advance of the game's next update.
For those who've played the game a while, you know the drill, but for anyone new to the RPG, let me explain. Every six weeks miHoYo hosts a livestream for each of its games, showing off what's arriving in the next update, including characters, quests, and events.
As a little incentive for people to watch, it gives out three codes you can redeem for some extra Primogems to use on pulling for the new characters.
Version 5.4 is adding the anemo five-star and wonderfully named Yumemizuki Mizuki, while it looks like we'll also see reruns for Wriothesley, Furina, and Sigewinne, if predictions are anything to go by.
I'll add each code to the list below as it goes live during the stream, and further down the page I'll explain your methods for redeeming it in case you're new to all this, or just want a quick link to the code redemption site.