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polarsource/polar

Open-source billing platform for AI and software products, handling usage-based pricing, subscriptions, checkout and merchant-of-record tax duties.

Open-source alternative to:Stripe BillingPaddle

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What is it?

Polar is a billing platform aimed at developers building AI products and other software that charges for usage. It covers metered billing for tokens, API calls, agent runs, GPU time and storage, alongside subscriptions, seats, credits, trials and discounts that can be combined into one pricing model.

Polar acts as the merchant of record, so it handles customer accounts, receipts, dunning and sales tax or VAT on the seller's behalf. The README also describes checkout flows, realtime metrics and a public API with webhooks for integrating billing into existing services.

The project is written mainly in Python with a TypeScript and Next.js frontend, and is built as a Turborepo monorepo. Official SDKs are provided for JavaScript and Python.

Key features

  • 01Usage-based billing for tokens, API calls, agent runs and GPU time.
  • 02Subscriptions, seats, credits, trials and discounts that can be combined.
  • 03Checkout flows with worldwide tax handled by the merchant of record.
  • 04Public API and webhooks for integrating billing into your services.
  • 05Official JavaScript and Python SDKs.

Use cases

  • An AI startup charging customers per token or per agent run.
  • A SaaS product moving from flat subscriptions to hybrid usage pricing.
  • A developer selling digital products without handling sales tax directly.

Things to know

  • Hosted service takes a per-transaction fee (5.00% + 50¢ on Starter, down to 3.40% + 30¢ on Scale), and additional fees may apply.

Topics

#payments#billing#subscriptions#usage-billing#saas#fastapi#nextjs#typescript#digital-products#merchant-of-record

FAQ

What is polar?
Open-source billing platform for AI and software products, handling usage-based pricing, subscriptions, checkout and merchant-of-record tax duties. Polar is a billing platform aimed at developers building AI products and other software that charges for usage. It covers metered billing for tokens, API calls, agent runs, GPU time and storage, alongside subscriptions, seats, credits, trials and discounts that can be combined into one pricing model.
Is polar free to use? What license does it have?
polar is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is polar still maintained?
Actively maintained. The last commit to polar was on Nov 6, 2026.
What can I use polar for?
An AI startup charging customers per token or per agent run. A SaaS product moving from flat subscriptions to hybrid usage pricing. A developer selling digital products without handling sales tax directly.
Where can I get polar?
The source code and installation instructions are on GitHub: https://github.com/polarsource/polar

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