$7,000 of Coffee in Two Days: an API to Check the Balance of One Developer's Active Starbucks Card

Jonathan Stark's Starbucks card is seeing a lot of use this week. That's because he's sharing it with the whole Internet. Anonymous people are both using and adding money to the card and we can all follow the balance with the Jonathan's Card API or over the tweets which come rolling in once per minute.

Anyone can download an image of Stark's card and use it on a mobile device capable of displaying the image to make a purchase. And using the card number, anyone can add money at Starbucks' website. Stark seeded the card with $300, but there has already been over $7,000 of purchases run through the card in what Stark calls "an experiment in social sharing of physical goods using digital currency on mobile phones."

Before Stark chose to make the experiment public, he decided to build an API to get at the data. "It was a preemptive move given that I knew I would get questions from people interested in seeing the data and building something with the data," Stark said. He had the idea on a Saturday night and took about a day to build what he calls a "super easy" project.

Already many developers have built ways of visualizing the data. The Atlantic charted the balance over time (see above), showing the effects of a Hacker News item and a Techcrunch post.

To get at the data which powers Stark's API, he has to scrape the Starbucks website once per minute. That's because Starbucks doesn't have a public API. "I can imagine use cases where developers could build an app on top of the Starbucks API," Stark said. "Instead of releasing an app they could release an API and let developers build on top of it."

"My total dream would be if they contacted me and said 'how should we set up our API,'" Stark said. He would want transaction and location data from a proper Starbucks API, something that he doesn't currently get by scraping. He admits Starbucks might not provide it because most people already know where they bought coffee and how much it cost. "Well, I don't," he said.

Stark hopes others will make their cards available similarly, perhaps with smaller groups rather than the whole Internet. He is planning to open source his code once he has removed any personal details like API keys from the code. If you're interested, watch his Github page.

But how much longer will his card be available? "I think the experiment itself will continue as long as someone will keep putting $10 on it," Stark said. And according to Stark, who has kept his contributions to the initial $300, if the balance ever remained $0 for long, he'd pony up more cash himself, just to keep it going.

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