Online shoppers now have a new tool to help them save money at checkout, without having to do much work at all. Recently launched shopping companion Zinc helps you automatically find the best price for the items in your shopping cart, and then pay however you want, including via Bitcoin or Dwolla.

The service, which works as either a Google Chrome extension or browser bookmarklet, is currently supported on major retailer’s sites, including Amazon, Walmart, Macy’s, and Target.

The Y Combinator-backed startup, founded by three friends from MIT, Max Kolysh, Doug Feigelson and John Wang, emerged from an earlier idea they had about building an API for buying things online. “A lot of online retailers have APIs for data retrieval, but they don’t have APIs for actually making the purchase. We thought it would be cool to create that for them, as a third-party,” explains Kolysh.

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