Square APIs and SDKs
Provider 
Founded 2009
Sells To Individuals, SMB
Pricing Model Transactional Commission
Ownership Public

Developer APIs and SDKs for custom Square commerce apps and integrations.
Square’s developer platform supports custom integrations across payments, orders, catalogs, inventory, customers, staff, reporting, and commerce.
The official offering describes more than 20 APIs and 100-plus endpoints, including restaurant-kiosk and custom-reporting use cases.
Flutterwave

Payments API Platform
flutterwave.com
MarginEdge

Public API
marginedge.com
Stripe

Stripe Payments
stripe.com
| Attribute | Square APIs and SDKs | Payments API Platform | Public API | Stripe Payments | |
|---|---|---|---|---|---|
| Provider | |||||
| Founded | 2009 | 2016 | 2015 | 2010 | |
| Sells To | Individuals, SMB | Enterprise, Small Business | Small Business | Enterprises, SMB | |
| Pricing Model | Transactional Commission | Recurring, SaaS, Transactional | Recurring | Recurring, Transactional, Usage-based | |
| Ownership | Public | Equity, Venture Capital | Venture-backed private company | Private Equity, Venture Capital |
Provider 
Founded 2009
Sells To Individuals, SMB
Pricing Model Transactional Commission
Ownership Public
Provider 
Founded 2016
Sells To Enterprise, Small Business
Pricing Model Recurring, SaaS, Transactional
Ownership Equity, Venture Capital
Provider 
Founded 2015
Sells To Small Business
Pricing Model Recurring
Ownership Venture-backed private company
Provider 
Founded 2010
Sells To Enterprises, SMB
Pricing Model Recurring, Transactional, Usage-based
Ownership Private Equity, Venture Capital

Coinbase Developer Platform

Affirm for Merchants
affirm.com

Unified Business Software API

Afterpay for Business
afterpay.com

Offers as a Service
fidelapi.com

Rutter Unified API

Payment Acceptance
xendit.co

NextAPI
nextpay.ph

Synctera Platform
synctera.com

Visa Offers Platform
developer.visa.com

Sezzle for Merchants
sezzle.com

GraphConnect API