Update: This method no longer works. (link)
It’s now possible to check Amazon gift card balances online while logged into your Amazon account, without having the balance applied to your Amazon account.
One of the quirks of Amazon gift cards and a few other gift card brands (iTunes comes to mind) is that it was never possible to check the balance of a gift card – all you could do was apply it to your account. This isn’t a big deal since the Amazon system is set up that gift cards are redeemed and combined into your Amazon balance; you don’t have to apply it to each purchase separately. It was still an inconvenience in some circumstances, particularly, if you want to resell the Amazon gift card, it’s more difficult without being able to verify the balance.
Amazon has now updated their system so that you can check the balance without applying it to your account.
As part of the regular ‘Redeem Gift Card’ system, it now gives us the option to applying the gift card or just to check its balance without applying it.
HT: Jake from Giftcardmart