Lago

Lago is open-source billing infrastructure for usage-based and subscription pricing models. It meters product usage - such as API calls, compute time, or LLM tokens - and turns that usage data into pricing calculations, credits, entitlements, invoices, and payment collection, rather than requiring a team to build metering and invoicing logic on top of a generic payments API.

It can be used directly as your own billing system (Lago Direct) or embedded to power billing for your own customers (Lago Embedded), and is used in production by companies including Mistral AI, Groq, and Synthesia for usage-based and AI-product billing specifically. The project positions itself for agentic and AI-product monetization as much as traditional SaaS subscriptions.

Lago is a fit for teams that need to bill based on metered usage rather than flat subscriptions, or that want an open-source alternative to hosted usage-billing platforms.