If you’re running your SaaS on Stripe Billing, it probably worked fine when your product was seat-based and simple. But as your pricing matured into usage-based, credit-driven, or feature-limited models, you’ve likely hit its limits.

Stripe was built for static subscriptions, not dynamic usage streams or real-time credit systems. And that’s where most teams start looking for open-source alternatives tools that give full control over data, pricing logic, and infrastructure without the trade-offs of vendor lock-in.

In this guide, we’ll explore the best open-source tools for subscription billing management in 2025 starting with Flexprice, a developer-first billing and metering platform designed for AI, API, and modern SaaS products that need flexibility, transparency, and precision at scale.

TL;DR

• Stripe Billing is great for simple subscriptions but struggles when your SaaS and AI products evolve into usage-based, hybrid, or credit-driven models.

• Developers increasingly are looking for open-source alternatives to avoid vendor lock-in, high fees, and limited flexibility.

• Flexprice leads this new wave as a developer-first, open-source billing and metering platform built for AI, API, and SaaS products. It supports real-time event tracking, hybrid pricing, credit wallets, and feature entitlements.

• Flexprice can be self-hosted or managed, giving full control over your data, logic, and pricing experiments.

• Kill Bill remains the most mature option but requires heavy engineering maintenance.

• BillaBear is a modular billing platform ideal for teams seeking self-hosted simplicity.

• Hyperswitch handles payment management (not billing); best paired with tools like Flexprice.

• Crater focuses on invoicing and accounting automation for small businesses, not complex SaaS metering.

If you’re scaling a usage-based or AI-native product, Flexprice is the most flexible, transparent, and future-ready open-source alternative to Stripe Billing.

Core Features to Evaluate Before Choosing a Billing Alternative

1. Usage-based and event-driven billing

Your SaaS or AI product needs the ability to ingest high volumes of events called in a quick and efficient manner. Whether its  API calls , token usage, compute hours and so on, your tool should count them and aggregate them into billable events. This will eradicate the possibility of revenue leakage.

2. Credit and wallet management

If your tools give you credits, you require a native wallet to manage those credits. The system should automatically deduct the credits as users avail your service and trigger auto top-ups for seamless transactions.

3. Support for Multiple Pricing Models

Your billing tool should support your billing logic; subscriptions, usage-based billing, overage billing or whatever your billing logic is. A flexible system lets you define hybrid models natively, making it easy to mix flat fees, per-unit pricing, and credit consumption while keeping invoices consistent and automated. 

4. Feature Entitlements and Access Control

As your SaaS grows, not every customer needs to view every feature. A decent billing system has to provide a way to define and enforce entitlements, the specific features, quotas, or usage limits for each plan or customer. 

This lets you gate on plan tier, region, or contract terms so customers only see what they are paying for. Entitlements also enable automatic upgrades, overage charging, and compliance enforcement, keeping your pricing intact and your customer experience transparent.

5. Integration, Security, and Hosting Flexibility

Your billing system should be able to integrate smoothly with your CRM, payment gateways, tax engines, and accounting systems to ensure revenue data consistency across the stack.

It should also allow secure data handling, like encryption, access controls, and audit logs to meet compliance standards like SOC 2 or ISO 27001.

Finally, flexibility is crucial, choose a platform that offers self-hosted and managed deployment options so that you can choose between full data ownership on your stack or the convenience of managed cloud space with scaling

Best Open-Source Alternatives to Stripe Billing

1. Flexprice

Flexprice is an open-source platform for metering, billing and feature management, built by developers, for developers. It handles the heavy lifting of usage tracking, feature access, and billing logic so you don’t have to build them from scratch.

Key Features

• Real-time event ingestion and aggregation for usage tracking

  Flexprice facilitates real-time data ingestion and aggregation. In simpler terms, think of it as a smart meter that records events instantly and sums them up. This way at any given point of time, you know what your customer is using.

  
  

• Hybrid Pricing

  Flexprice supports hybrid pricing where you can charge your users a fixed price, extra charges based on usage, credits that they can spend, and overage charges if they go beyond their limits. 

  
  

  Stripe is built natively for seat-based pricing and it cannot handle complex logics like hybrid pricing. Flexprice makes this simple by combining all these models in one place so you can offer flexible plans that grow naturally with each customer’s usage. 

  
  

• Credit wallet with auto top-up and expiration management

  A credit wallet is like a virtual account for every user where they can store and use credits towards various kinds of transactions with Flexprice. You can manage prepaid credits for your customers. 

  
  

  Wallets ensure efficiency and  transparency in credit handling. These wallets have defined currency and can be topped up manually or automatically. Stripe supports one-time credits only. 

  
  

  Stripe lacks an in-built credit rollover system implying that it needs manual rigor to manage credits in billing whereas Flexprice facilitates rollover of these credits with certain expiration rules.

  
  

• Feature gating and entitlements per plan or customer

  Flexprice helps you grant or restrict access to features for your users at an individual level. This ensures every user gets the right capabilities without maintaining multiple product versions. 

  
  

  Stripe is not equipped with feature level entitlements, it can only be useful for billing volumes of events called whereas Flexprice has its billing and entitlements logic in one place which gives you real-time feature gating.

  
  

• Self-hosted or managed deployment options

  Flexprice can be self-hosted on your infrastructure with full data control and customization or you can choose the managed cloud version to avoid operational overhead. 

  
  

  By self-hosting, you get a free hand at inspecting and modifying your platform. This provides freedom to pursue your own billing logic while benefitting from the community insights.

  
  

  Flexprice is built for modern AI, API, and SaaS businesses that need flexible pricing models, real-time usage metering, and self-serve billing workflows. Whether you charge per API call, per token, per user, or through credits, Flexprice gives you the structure to experiment, iterate, and scale your monetization without engineering bottlenecks.

  
  

• Freedom from vendor lock-in

  Flexprice gives you the flexibility to switch payment processors. You can use Stripe, RazorPay, or any payment gateway for that matter. This gives you an edge at scalability without getting locked with the stack. Stripe on the other hand, doesn't give you that flexibility to be able to collect payments from various gateways.