Be careful if you purchased a key from an international seller. Steam keys are often region-locked. If you try to redeem a key intended for North America on an account based in Europe (or vice versa), the mobile system will reject it.
If you prefer using the app, the option is tucked away inside the Wallet section. Open the Steam Mobile App on your Android or iOS device. Tap the (menu) or your profile icon. Navigate to Store > Wallet . Select Redeem a Steam Gift Card or Wallet Code . steam key on mobile
If you successfully redeemed the key on your phone but can't see the game immediately, don't panic. Be careful if you purchased a key from