Open-Source Alternatives to Square

Books is double-entry accounting software designed for recording business transactions and managing a general ledger. It functions as an invoicing and billing platform to track accounts payable and receivable, and as a financial reporting tool for generating balance sheets and profit and loss statements. The application is built as an offline-first bookkeeping system that stores data locally during internet outages and synchronizes changes once connectivity is restored. It also includes a retail point of sale system to process immediate sales and record inventory movements. The software cove

BTCPay Server is a non-custodial payment gateway and invoice manager designed for accepting Bitcoin and other cryptocurrencies directly into a private wallet. It serves as a self-hosted payment infrastructure that allows merchants to manage digital invoicing and storefronts without relying on third-party intermediaries. The system distinguishes itself through a non-custodial wallet architecture that ensures private keys remain on the user's own hardware or server. It integrates the Lightning Network for instant, low-cost transactions and provides a hardware-wallet signing bridge to secure tra

Jeepay is an open-source payment gateway that accepts payments through WeChat Pay, Alipay, and UnionPay from a single integrated system. It functions as a multi-channel payment platform with aggregated QR code generation, allowing customers to scan one code and pay with any supported method, while also providing multi-merchant account management for onboarding and isolating independent merchants with their own payment configurations. The system secures all API requests and responses using cryptographic signatures to verify authenticity and prevent tampering. It delivers asynchronous payment r

Active Merchant is a Ruby library that provides a payment gateway abstraction layer to process credit card transactions across multiple different payment processor APIs. It serves as a payment API wrapper, offering a consistent set of commands and classes that abstract the complexity of various provider request and response formats. The library utilizes a unified payment gateway API to standardize global payment processing and unify payment flows. It specifically includes a standardized interface for handling 3D Secure authentication and identity verification for card-not-present transactions

Bank is an open-source financial web application that provides double-entry bookkeeping, multi-currency transaction processing, and localized banking interfaces. It maintains accurate financial records and account balances using formal accounting rules, storing every financial operation as balanced debit and credit entries in the database. The software processes monetary transactions in various currencies by fetching live exchange rates via external application programming interfaces. It adapts to international users through localized interface translations across multiple human languages.

Invoice Ninja is a professional billing and invoicing platform designed for managing clients, projects, and financial records. It serves as a multi-currency billing system and time tracker available as both a cloud-based application and a self-hosted suite. The platform distinguishes itself through comprehensive support for regional taxes, diverse currency formats, and automated exchange rate updates. It includes dedicated cross-platform mobile and desktop applications to manage business data across different operating systems. The software covers the end-to-end financial lifecycle, includin

Idurar is an integrated system combining Customer Relationship Management and Enterprise Resource Planning. It functions as a headless business API that generates secure REST endpoints and administrative panels from configuration files to connect business logic with external applications. The platform supports multi-tenant SaaS management, isolating data and configurations for multiple companies or branches within a single installation. It is designed for international business accounting, featuring a multi-currency financial engine that processes transactions and manages regional tax rules a

eShop is a .NET microservices reference application that provides a comprehensive blueprint for a distributed retail system. It implements an e-commerce architecture using decoupled services to manage core operations such as product catalogs, shopping baskets, and order processing. The project demonstrates a cloud-native retail infrastructure that incorporates an asynchronous event bus system to synchronize state across distributed services. It includes a reference implementation for integrating generative AI features by connecting the store to large language models via cloud providers. The

This project is a Kubernetes microservices reference architecture implemented as a functional cloud-native e-commerce demo. It serves as a distributed systems testbed designed to demonstrate cloud-native deployment patterns, orchestration, and the interaction of independent services. The system showcases a polyglot service implementation using high-performance communication via gRPC and REST. It integrates generative AI for image analysis and product recommendations, and implements a service mesh to manage traffic, security, and observability between services. The application covers e-commer

yii2_fecshop is a comprehensive B2C e-commerce platform and CMS built on the Yii2 PHP framework. It functions as a headless commerce API and an international storefront solution, supporting both single-vendor stores and multi-vendor marketplaces where independent merchants can manage their own products and orders. The system is distinguished by a multi-entry point architecture that separates administrative, web, mobile, and API interfaces while sharing a common service layer. It provides high extensibility through configuration-driven service replacement, event-driven functional extensions, a

This project is a PHP e-commerce platform and enterprise storefront framework designed for building and managing online stores. It functions as a modular PHP application and headless commerce engine, separating e-commerce business logic from frontend presentation to support multiple storefronts and devices. The system is built on a modular architecture that allows developers to add custom business logic and third-party integrations. It utilizes a service-contract-based API to ensure stability across module implementations and employs dependency-injection for object lifecycle management. Core

Openblocks is a low-code platform for building custom internal tools. It provides a visual interface where users can assemble applications by dragging and dropping pre-built components onto a canvas, connecting them to databases and APIs without writing code. The platform distinguishes itself through its architecture for embedding and reuse. Entire application pages can be rendered as native React components inside other applications, replacing traditional iframe-based embedding. Custom components and queries can be bundled into reusable modules for use across multiple applications, and an au