Open-Source Alternatives to PayPal

Crater is an invoicing and billing software system designed for creating professional invoices, estimates, and recurring billing schedules. It serves as a multi-entity accounting manager, allowing for the organization and separation of financial data and billing records across multiple different business organizations. The platform integrates payment gateway services to collect funds directly from customers and provides a secure client billing portal where customers can access account details and pay outstanding invoices. It also functions as an expense tracking application to log outgoing co

Crater is an open-source invoicing and expense tracking software designed for individuals and small businesses. It serves as a self-hosted billing platform that allows users to monitor the overall financial health of a business by recording professional services rendered and tracking outgoing costs. The system functions as a payment gateway integrator, connecting to third-party providers such as Stripe to process secure transactions for issued invoices. It provides specialized tools for freelance invoice management, including the generation of professional billing documents and cost estimates

Crater is an open source invoicing software and multi-tenant accounting system. It serves as a financial management tool for creating professional invoices and estimates, tracking business expenses, and managing the financial records of several distinct business entities within a single instance. The platform integrates with payment processors to collect client payments automatically and provides a dedicated billing portal where customers can access their history and pay invoices online. It includes a template-based engine for generating PDF invoices and supports the automation of recurring s

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

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

Roncoo Pay is a multi-tenant payment platform that integrates Alipay and WeChat Pay as external payment channels, handling payment request routing, authorization, and capture. It also includes an automated settlement engine that calculates net amounts and initiates daily fund transfers, along with a reconciliation engine that matches internal transaction logs against provider statements to detect discrepancies. In addition to payment processing, the project provides a multi-tenant online education delivery platform for live and on-demand courses, exams, and enterprise training. The platform u

Polar is a digital product monetization engine and subscription management system. It serves as a merchant of record platform that handles global sales tax and VAT compliance, providing the infrastructure for selling subscriptions and one-time digital goods via hosted checkouts and embedded payment flows. The project functions as an entitlement and access manager, automating the granting and restriction of digital benefits, license keys, and third-party platform roles. It includes a dedicated usage-based billing infrastructure that tracks customer activity through meters to apply aggregation

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

Lago is an open-source billing platform designed for managing subscriptions, usage-based metering, and automated invoicing. It functions as a comprehensive system for defining pricing plans, tracking real-time consumption via a metering engine, and controlling feature entitlements based on active customer subscriptions. The platform differentiates itself through a dynamic billing engine that supports hybrid pricing models and a credit-based wallet system for managing prepaid funds. It includes specialized tools for multi-tenant entitlement mapping, allowing operators to tie specific product p

Akaunting is a modular business enterprise resource planning system and self-hosted accounting software. It provides a comprehensive platform for small business financial management, centering on a double-entry bookkeeping system with a general ledger and chart of accounts. The platform is designed for extensibility through a module-based architecture and a dedicated marketplace for procuring third-party applications. It supports multi-tenant data isolation and utilizes role-based access control to manage granular user permissions. Its capability surface covers a wide range of business opera

Kill Bill is a subscription billing platform and usage-based billing engine designed to manage recurring invoicing and automated payment collection. It functions as a multi-tenant billing infrastructure, providing isolated environments for different organizational entities through a dedicated API. The system is distinguished by a plugin-based extension framework that allows for the integration of third-party payment gateways and custom business logic. It includes a payment gateway orchestrator to handle transactions and refunds, as well as a revenue recognition system to allocate contract rev

Hyperswitch is a payment orchestration platform designed to manage complex transaction lifecycles through a centralized control layer. It functions as a processor-agnostic integration hub that standardizes disparate external payment APIs, allowing businesses to route transactions across multiple providers to optimize for authorization rates and cost efficiency. The platform utilizes a state-machine-based architecture to track every payment from initial authentication to final settlement, ensuring consistent processing and reliable error recovery. What distinguishes the platform is its intelli