CreditKit

CreditKit is a starter template that gives developers a working usage credits billing system built on Next.js, Supabase, and Stripe. If you're building an AI application and need users to pay per generation, per API call, or per task rather than a flat monthly fee, this template handles the plumbing so you don't have to wire it together yourself.

Usage based billing sounds simple until you actually try to build it. You need to track credits atomically so partial failures don't leave users overcharged or undercharged. You need webhooks that can be retried safely without double charging. You need background jobs that refund credits when something goes wrong. CreditKit ships with all of this already working. The credit spend is atomic, meaning the transaction either completes fully or rolls back entirely. The Stripe webhooks are idempotent, so retrying them won't duplicate charges. And there's a background worker that watches for failed jobs and processes refunds automatically.

The stack choices make sense for the audience it's aimed at. Next.js handles the frontend and API routes. Supabase provides the database and auth layer. Stripe does the actual payment processing. If you're already comfortable with this stack or planning to use it anyway, adding CreditKit means you skip weeks of integration work and start with a billing system that's already tested.

What you're buying is the source code outright. It's not a subscription or a hosted service. You pay the one time price, download the code, and own it. You can modify it, extend it, or rip out pieces you don't need. There's no ongoing fee and no dependency on a third party staying in business.

The template is aimed at indie developers and small teams building AI products where per use pricing makes more sense than subscriptions. Think image generators, document processors, code assistants, or anything where the cost to you scales with usage and you want the pricing to your users to match. If you've been putting off usage billing because it felt like a distraction from the actual product, this is the shortcut.

The pricing is a one time $129. That gets you the full source code with no restrictions. Compared to the time it takes to build a robust credits system from scratch, handle edge cases around failed transactions, and test Stripe webhook retry behavior, the math works out quickly if your time is worth much at all.

CreditKit doesn't try to do everything. It's specifically a billing and credits layer, not a full SaaS boilerplate with user management, dashboards, or landing pages. That narrow focus is a strength if you already have opinions about the rest of your stack, but it does mean you'll need to bring your own frontend components and user interface beyond the billing flow.