Developer Glossary
Square is a financial services and payments platform that started with a tiny white card reader and grew into a comprehensive ecosystem covering point-of-sale hardware, online payments, invoicing, payroll, banking, and business analytics. For custom web application development, Square's APIs are particularly strong for businesses that need to bridge the gap between in-person and online transactions. The Square Payments API handles card processing with clean, well-documented endpoints, while the Catalog, Inventory, and Orders APIs let you build custom storefronts and management tools that stay in sync with a merchant's physical Square terminal. The developer experience is notably good, Square's sandbox, documentation, and SDKs for Node.js, Python, Ruby, and PHP are consistently among the best in the payments industry. If a client runs Square for their brick-and-mortar operations and needs a custom web app, integration is straightforward.
Square was founded in 2009 by Jack Dorsey (who was also co-founding Twitter at the time) and Jim McKelvey, a glassblowing artist from St. Louis. The origin story is one of the best in tech: McKelvey lost a $2,000 sale on a piece of art because he couldn't accept credit cards. He told Dorsey about it, and together they prototyped a tiny card reader that plugged into a phone's headphone jack. The first reader was literally carved out of a block of wood as a prototype. They launched the product in 2010, and it was an instant hit with small businesses, food trucks, farmers' market vendors, and independent contractors who had never been able to accept card payments before. Square went public in 2015, and in 2021 the parent company rebranded to Block, Inc. to reflect its expansion into cryptocurrency (Cash App), music (Tidal), and decentralized technologies.
The original Square card reader was designed to be the exact dimensions of a square, that's where the company name comes from.
The original Square card reader was designed to be the exact dimensions of a square, that's where the company name comes from. Jim McKelvey, the co-founder, is a trained glassblower who still practices the craft and has written a book called "The Innovation Stack" about the dozens of interlocking innovations Square had to create simultaneously to make the product work (including building their own fraud detection system from scratch because existing ones rejected too many legitimate small-business transactions). Also, Square's first office was in Jack Dorsey's apartment in San Francisco, and the very first Square transaction was made in February 2010 by a friend buying a cup of coffee for $1. The company processed $1 billion in payments within its first year.
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