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As quick service chains try to differentiate themselves, delivery has emerged as a major battleground. Increasingly, it isn't a question of who delivers, but who isn't thinking about trying to do so.

The fast-food and fast-casual industry is quickly evolving to adapt to new tech, from mobile ordering to the rise of delivery apps like Seamless. These new developments go hand-in-hand with new ways to deliver food – platforms that make delivery possible for restaurant chains that never previously thought delivery was a viable option.

Here are six chains that recently revealed plans to start testing delivery.

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Dunkin' Donuts

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Dunkin' Brands CEO Nigel Travis revealed in early June that the company is privately testing delivery. While the public won't have a chance to have doughnuts and coffee delivered to their door for a while, the chain has launched a new mobile payment option – Visa Checkout – that may help pave the way for mobile ordering down the line.

Taco Bell

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The taco chain isn't rolling out all-day delivery yet, but as of late May, the chain is testing delivery near college campuses, reports The Street. Yum Brands CEO Greg Creed said that he wouldn't rule out the possibility of delivery services from Taco Bell's sister company KFC either, meaning the chicken chain may soon also start delivery tests of its own.

McDonald's

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In May, McDonald's began offering delivery in New York City, through a partnership with Postmates. For McDonald's, delivery is part of a larger "experience of the future" effort that attempts to revitalize the brand's image with tests such as all-day breakfast and the premium, customizable "Taste Crafted" menu platform.

Related: Obama's Ex-Press Secretary Is Now Working at McDonald's

Chipotle

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On Monday, Dunkin' Brands CEO Nigel Travis revealed that the company is privately testing delivery. While the public won't have a chance to have doughnuts and coffee delivered to their door for a while, the chain has launched a new mobile payment option – Visa Checkout – that may help pave the way for mobile ordering down the line.

Panera

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Panera has been testing delivery for the past year in some key markets, but the fast-casual chain is ready to heat up the delivery scene in 2015, with 28 delivery hubs open as of late April. In April, the chain announced that it is expanding its delivery test and plans to roll out the option more broadly next year. Panera hasn't yet settled on a delivery model, testing models that use third-party drivers as well as models that uses company drivers, and unlike other chains, has emphasized catering throughout the delivery test process.

Starbucks

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In March, the coffee chain announced it was testing two delivery models in two cities: Seattle and New York City. In Seattle, Starbucks teamed up with Postmates to integrate delivery into the company's mobile app. In New York City, Starbucks eschewed partners in favor of the "Green Apron" option that allows customers in select office-buildings to order food and drinks to be delivered by Starbucks barisitas.

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