> ## Documentation Index
> Fetch the complete documentation index at: https://docs.therius.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Therius Payment API — Developer Documentation Home

> Accept cards, wallets, and 40+ alternative payment methods globally with a single unified API. Get your first payment through in minutes.

Therius is a payment API that lets you accept cards, digital wallets, and over 40 alternative payment methods — Pix, ACH, iDEAL, Klarna, Apple Pay, and more — through a single endpoint. This documentation covers everything from your first sandbox call to managing subscriptions, handling 3D Secure challenges, and integrating the JS SDK for browser-safe card collection.

> **[Quick Start](https://docs.therius.io/quickstart.md)**
>
> Fire your first payment in under 5 minutes with nothing but a sandbox key and a terminal.

> **[Authentication](https://docs.therius.io/authentication.md)**
>
> Learn how API keys work, which key to use where, and how to pass credentials correctly.

> **[API Reference](https://docs.therius.io/api-reference/purchase.md)**
>
> Complete reference for every endpoint — purchase, authorize, capture, refund, and more.

> **[JS SDK](https://docs.therius.io/sdk/overview.md)**
>
> Collect card details safely in the browser using hosted fields or the drop-in Checkout Widget.

> **[Connections](https://docs.therius.io/connections/overview)**
>
> Browse the full catalog of payment methods — with working code examples for each.

> **[Subscriptions](https://docs.therius.io/guides/subscriptions.md)**
>
> Build recurring billing with plans, trials, dunning, pause/resume, and plan changes.

## How Therius Works

Every payment — card, wallet, or alternative method — flows through the same `/payment/purchase` endpoint. You choose the payment method by passing a `paymentMethod` field (or omitting it for cards). The response always has the same shape, so your backend doesn't need separate code paths per method.

**1. Get a sandbox key**

Your Therius account includes a sandbox key (`prv_sandbox_...`) out of the box. It routes to a test-provider stub — nothing touches a real card network.

**2. Make your first API call**

Send your key as `Authorization: Bearer prv_production_...` and fire a `POST /payment/purchase`. See the [Quick Start](https://docs.therius.io/quickstart.md) for a ready-to-run curl command.

**3. Integrate the JS SDK (if browser-based)**

If you're accepting cards from a browser, use the [JS SDK](https://docs.therius.io/sdk/overview.md) so raw card numbers never transit your server. The SDK issues a one-time nonce; your server charges the nonce.

**4. Go live**

Swap `prv_sandbox_...` for `prv_production_...` and point at `api.therius.io`. No other code changes required.

## Key Concepts

> **[Payment Lifecycle](https://docs.therius.io/concepts/payment-lifecycle.md)**
>
> Understand authorize, capture, refund, and cancel flows.

> **[Smart Routing](https://docs.therius.io/concepts/smart-routing.md)**
>
> Route each payment across your acquirers with conditions and cascading failover.

> **[Tokenization](https://docs.therius.io/concepts/tokenization.md)**
>
> Store cards as reusable tokens for returning shoppers.

> **[3D Secure](https://docs.therius.io/concepts/3d-secure.md)**
>
> Handle 3DS2 challenges without complex branching logic.

> **[Idempotency](https://docs.therius.io/idempotency.md)**
>
> Safely retry failed requests without double-charging customers.

> **[Environments](https://docs.therius.io/concepts/environments.md)**
>
> Switch between sandbox and production with a single key prefix.

> **[Alternative Methods](https://docs.therius.io/guides/alternative-payment-methods.md)**
>
> Add Pix, ACH, Klarna, and more with minimal extra code.

> **[Webhooks](https://docs.therius.io/webhooks/overview.md)**
>
> Receive signed payment and subscription events on your server.

> **[Testing](https://docs.therius.io/guides/testing.md)**
>
> Sandbox test cards, decline scenarios, and 3DS test flows.


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