Square has introduced a redesigned credit card reader that's thinner and more advanced than its predecessor.

The new Square is 45 per cent thinner than the original, making it as slim as the iPhone 5S, and has tapered edges that make it easier to swipe a card.

Speaking of swiping a card, the new Square has a bunch of tweaks that improve "the feel of the swipe," according to Wired.com, which has an in-depth feature on Square and the development process behind the redesigned card reader.

Beyond design, look and feel, the new Square has a number of under-the-hood improvements. Many of the internal components were replaced by custom-made parts. The magnetic read head is customised and able to be precisely soldered to the circuit board, for instance.

Square is now also compatible with more smartphones and tablets. The redesigned credit card readers has an enhanced audio plug connection that works with a wide array of devices. The new plug also allowed Square to drop the internal battery and two millimetres in size.

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The new Square is available now from the company's website. It will land on the shelves of more than 30,000 retail stores in 2014.