Square

API

Square is a financial services and payment platform providing POS systems, online payments, payroll, banking, and busine

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Last updated: April 2026

Square is a financial services and payment platform providing POS systems, online payments, payroll, banking, and business tools for merchants.

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ERP & Business OperationsSaaS Commercial

About

Square is a financial services and commerce technology company founded in 2009 by Jack Dorsey and Jim McKelvey. Starting with a simple card reader attachment for smartphones, Square has grown into a comprehensive business platform providing point-of-sale systems, online payment processing, payroll management, banking services, and a wide range of business tools for businesses of all sizes.

The Square Point of Sale (POS) system is the product that established Square's market presence and remains central to its platform. Square's hardware lineup includes the Square Reader (for magstripe and contactless payments), the Square Terminal (a standalone device for payments and receipts), the Square Register (a full checkout system with customer display), and the Square Stand (for iPad-based POS setups). All hardware connects to the Square software ecosystem for unified sales tracking, inventory management, and reporting.

Square Online provides e-commerce capabilities for merchants who sell both in-person and online. The website builder enables creating simple e-commerce stores that synchronize inventory with the Square POS, ensuring that stock levels are consistent across channels. Orders from the online store appear in the same Square Dashboard alongside in-person transactions, simplifying operations for omnichannel retailers.

The Square Developer Platform enables businesses to embed Square's payment capabilities into their own applications and websites. The Square Payments API accepts card payments, digital wallets, and ACH bank transfers. The Orders API, Catalog API, and Inventory API provide programmatic access to order management and product catalog functionality.

Square Payroll provides full payroll processing for employees and contractors, including automatic tax calculations, direct deposit, W-2 and 1099 filing, time tracking integration, and next-day direct deposit. The payroll service integrates with Square's time tracking tools, making it straightforward to run payroll based on tracked hours.

Square Banking offers business checking and savings accounts, instant access to same-day deposits from Square sales, and Square Loans which uses sales data to offer working capital financing based on the merchant's actual revenue history.

Square for Restaurants, Square for Retail, and Square Appointments are vertical-specific configurations of the Square POS tailored to the specific workflows of food service businesses, retail stores, and service businesses with scheduling needs.

Positioning

Square, now operating under parent company Block Inc., transformed small business payments by turning any smartphone or tablet into a point-of-sale terminal. What began as a simple card reader that plugged into a headphone jack has evolved into a comprehensive commerce ecosystem covering payments, banking, payroll, marketing, and online sales for businesses of every size.

Square's developer platform extends this ecosystem through APIs that enable custom payment integrations, inventory management, and customer engagement workflows. The platform processes billions of dollars in transactions annually and has become foundational infrastructure for millions of sellers worldwide.

What You Get

Payments API
Accept in-person, online, and in-app payments with a unified API that handles cards, digital wallets, ACH, and buy-now-pay-later through Afterpay
Square POS Hardware
Purpose-built terminals, registers, and readers designed for retail, restaurant, and service businesses with offline payment capability
Commerce Platform
Integrated tools for inventory management, online store, invoicing, and appointment scheduling connected to a single merchant dashboard
Banking Services
Square Banking with checking accounts, savings, instant transfers, and business loans based on transaction history rather than credit scores
Developer SDK
Client libraries for iOS, Android, and web with pre-built UI components for payment forms, in-app payments, and reader integration
Team Management
Employee scheduling, time tracking, payroll processing, and tip management integrated directly with sales data

Core Areas

Small Business Payments

End-to-end payment processing with flat-rate pricing and next-day deposits that eliminates the complexity of traditional merchant accounts

Restaurant Technology

Kitchen display systems, table management, online ordering, and delivery integration purpose-built for food service operations

Retail Commerce

Inventory tracking, purchase orders, vendor management, and barcode scanning for physical retail with e-commerce synchronization

Developer Integrations

APIs and webhooks for building custom commerce applications, marketplace payments, and embedded financial services

Why It Matters

Before Square, accepting card payments required a merchant account, expensive hardware, and complex processing agreements that excluded millions of small businesses. Square democratized payments with transparent pricing and hardware that cost a fraction of traditional POS systems, fundamentally changing who could participate in electronic commerce.

For developers, Square's APIs provide the same payment infrastructure that powers millions of sellers — enabling startups and platforms to embed professional-grade commerce capabilities without building payment systems from scratch.