As I mentioned before I have a Spotify premium account that I regularly pay for with gift cards. Spotify does not like that: if they could get ahold of my credit card number they could not only stop worrying that I won't pay them anymore but also they could track me better across the web - people change their e-mail all the time, but their credit card and cell phone numbers tend to last much longer. Or even better, maybe I'll stop using the service altogether but forget to cancel, which is as close as free money as one can get.

Given that Spotify does not like people using gift cards, they don't offer a way for you to redeem your gift cards directly via the app. This is annoying: I do not know my Spotify password (that's what my password manager is for) and therefore renewing my account requires me to go home and sit in front of my PC. If only there were a way for me to redeem gift cards directly from the app...

But guess what? There is. After some probing I have found the following steps that seem to work reliably in Germany:

1. Open the Spotify app, click on the "Settings" wheel and go to "Premium plan".
2. Choose any of the available premium plans, as if you were about to subscribe to one of them.
3. Choose "Credit Card" as payment.
4. Without entering any information scroll down and click on the "Terms and Conditions" link.
5. This will take you to a new window. On the top right you'll see your profile picture. Click on it and choose "Support".
6. This takes you to Spotify's Support page. Type "gift card" (or, in Germany, "Geschenkkarten") and click the first link that comes up.
7. The link will take you to an article explaining how to redeem gift cards, including a link to https://spotify.com/de/redeem. Click on it.
8. This will take you to the Gift Card redemption website, with the nice extra that you'll be already logged in. So enter the gift card code and you're done.

This stupidly long series of steps works because Spotify's internal browser already has your credentials (otherwise you'd need a password every time you open the app) and because the T&C page gets you out of the expected workflow that restricts what you can do. And given that we know the app has your account info, all Spotify would have to do to support gift cards is to add an extra button under their Premium plans saying "Redeem Gift Card" taking you there.

It is amazing the kind of thing your apps can do for you once you force them into compliance.