> For the complete documentation index, see [llms.txt](https://docs.tiun.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tiun.io/how-it-works.md).
# How it works
## The core flow
tiun replaces the commercial backend you'd normally build yourself. Instead of stitching together a payment provider, an auth system, session management, and access control — you create a product in the tiun dashboard, and the SDK handles everything from checkout to access.
The flow is simple: you define a **product** (a subscription plan, a one-time fixed fee, or a time-based rate), then call **checkout** (subscriptions and one-time purchases) or **start** (time-based) from your frontend. tiun takes over — it shows the payment UI, authenticates the user, processes the payment, and manages the session. Your app receives an event when **access** is granted, and you show the content.
There's no backend to build. No webhook endpoints to maintain. No user tables to manage. tiun is the layer between your frontend and all the commercial infrastructure — payments, identity, access control, customer data. You write product logic; tiun handles the commercial stack.
***
## What tiun manages for you
| Feature | What you get |
| ----------------------- | --------------------------------------------------------------------------------------------- |
| **Checkout UI** | Fully hosted payment overlay, no forms to build. |
| **Payment processing** | Cards (Visa, Mastercard, Amex), Apple Pay, Google Pay, PayPal and TWINT (region-dependent). |
| **Authentication** | Email + OTP login, no passwords. |
| **Session persistence** | Returning users are recognized automatically — sessions and payment connections are restored. |
| **Access control** | Entitlement state and paywall events, handled for you. |
| **Customer data** | Users, purchases, and revenue tracked in your dashboard. |
***
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