Fynex documentation
Fynex documentation
Build payments and billing into your product.
Explore guides for accepting payments, paying out to payees, and billing customers. One seller secret key authenticates both APIs.
Start here
Get your key, choose an integration, and make your first API call.
Get your API keyIssue credentials and learn how to authenticate.Start with PaymentsAccept money and pay it out: hosted checkout, server-to-server card payments, Apple Pay and Google Pay, split payments to marketplace payees, payouts and wallets.Start with BillingRaise and collect the documents that say how much: contracts, subscriptions, metered usage, invoices and credits.
Build by use case
- Accept payments onlineSend customers to a Fynex-hosted payment page; card data never reaches your servers.Payments
- Build a marketplaceSplit each payment between your platform and the sellers on it.Payments
- Pay payeesMove money from a seller wallet to a payee's bank account.Payments
- Set up usage-based billingReport metered usage and bill it on invoices.Billing
- Reconcile paymentsCompare settled funds with what arrived in your bank account.Payments
Browse by product
Fynex Payments API
Accept money and pay it out: hosted checkout, server-to-server card payments, Apple Pay and Google Pay, split payments to marketplace payees, payouts and wallets.
Get started
- Fynex Payments API
- Getting started
- Quickstart
- Concepts & Domain Entities
- Authentication & Tokens
- Test cards & sandbox
- Going live
Checkout & payment methods
- Hosted checkout
- Embeddable checkout widget
- Server-to-server payments
- Payment methods & capabilities
- 3DS Authentication
- Apple Pay
- Google Pay
- Alternative payment methods (APM)
- Recurring payments
Marketplace & payouts
Operate payments
Fynex Billing API
Raise and collect the documents that say how much: contracts, subscriptions, metered usage, invoices and credits.
Get started
Plans & billing
Usage
Operate
Reference
API reference & resources
Look up endpoints and schemas, generate a client, or read the complete reference.
Fynex Payments API
Fynex Billing API
For coding agents
- What is on this host, and the mistakes to avoid
- Every reference inlined, so an agent needs one request
- Task-shaped skills for Claude Code, Cursor and other agent clients
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