Square offers integrated card readers, terminals, and online payment processing for US businesses. Pricing is flat-rate per transaction with no monthly fee on the free plan and no lock-in contract, which makes it the most common starting point for small US merchants accepting card payments.
The free POS app, free magstripe reader, and same-day onboarding remove most of the friction of getting set up. Paid plans add advanced features per location, and the rate is higher than a negotiated interchange-plus deal at scale, but for most small businesses the simplicity wins.
Square was founded in 2009 and is headquartered in San Francisco, USA.