What it is

Polar is an open-source billing platform and payment infrastructure project for digital products, SaaS applications, and AI workloads. It is written in Python, licensed under Apache-2.0, and built around FastAPI, Next.js, React, and Turborepo. The project positions itself as a financial layer for software that needs to charge for tokens, agents, compute, subscriptions, and usage-based models.

The concrete problem it addresses is the billing boilerplate that product teams otherwise build and maintain themselves. Instead of assembling pricing logic, metering, checkout, receipts, dunning, customer accounts, tax handling, and merchant-of-record responsibilities from scratch, a team can adopt Polar as a payments platform. Its topics point to an ecosystem of digital products, subscriptions, merchant-of-record services, and API-driven payment workflows.

Key capabilities

• Polar supports usage billing, subscriptions, seats, credits, trials, and discounts, so a product can compose the pricing model it needs.
• It can meter tokens, API calls, agent runs, GPU seconds, and storage with event-level precision.
• It provides checkout flows, realtime metrics, and worldwide tax handling as part of the billing platform.
• It can operate as a merchant of record, handling receipts, customer accounts, dunning, sales tax, and VAT.
• It supports AI workload billing patterns, including metered token billing on model calls, per-run agent billing with step-level granularity, and retries without double-billing.
• It exposes a Public API, Webhook API, and official JavaScript and Python SDKs for integration.

Who uses it and how

• AI startups use it to turn usage into revenue by charging for tokens, agents, and compute without building internal billing infrastructure.
• SaaS and digital-product teams use it to ship pricing models such as subscriptions, seats, credits, trials, and discounts.
• Developers integrate Polar into docs, sites, or services through the Public API, Webhook API, and JavaScript or Python SDKs.
• Product owners can rely on merchant-of-record workflows to offload receipts, customer accounts, dunning, sales tax, and VAT.

Getting started

The README points to the website, docs, and API reference, and lists Starter, Pro, Growth, and Scale plans. For local development, it directs users to DEVELOPMENT.md, while integration can begin with the Public API, Webhook API, and official JavaScript or Python SDKs.

When to use it — and when not to

Polar is a good fit when an AI or SaaS product needs metered billing, merchant-of-record handling, and API integration rather than building billing infrastructure internally. It is less suitable when a team requires a complete self-hosted installation guide from the README, because the excerpt gives pricing and development pointers but no Docker images, package-manager commands, or required database, storage, and SMTP services. The repository metadata shows a zero-year age, zero listed contributors, and 141 open issues, which may make teams cautious about adopting it for critical payment workflows.