Genshin Impact, Honkai: Star Rail and Zenless Zone Zero all have a web redemption page, so codes can be entered without launching the game. Wuthering Waves is in-game only, and Cookie Run: Kingdom works only on the DevPlay web page. Below are the exact steps and pitfalls for each title. For codes that work right now, grab them with one-click copy on the coupons page.
Unlike the HoYoverse titles, Wuthering Waves has no web redemption page. Codes can only be entered inside the game.
Cookie Run: Kingdom coupons can be redeemed only on the official DevPlay coupon page (there is no in-game field). A DevPlay account is required.
NIKKE has no web redemption page — copy the code and redeem in-game. One use per account; codes can expire without notice.
Coupons expire without notice. Codes revealed during version preview livestreams are often valid for only a day or two, so redeeming the moment you see one pays off. Codes are case sensitive, so copy and paste beats typing them out, and each code works once per account. Variants of an expired code will not register, so lean on the coupons page, which keeps only verified, current codes — with one-click copy and [Redeem →] links that auto-fill the code.