Introduction

Developer documentation for the halfin cryptocurrency payment API.

halfin gives merchant developers API primitives for creating addresses, invoices, and payouts — plus the supporting surfaces to run them safely: balances, transactions, rates, currencies, and webhooks.

All requests authenticate with an API key in the X-API-Key header. Test keys (sk_test_...) are isolated from live keys (sk_live_...) with no cross-environment data leakage.

Get started

Quickstart

Create a first invoice in the sandbox in about 5 minutes.

Authentication

API key format, environments, and security practices.

Environments

Production and sandbox base URLs.

Resources

Invoices

One-time payment requests — create, track, and cancel.

Addresses

Reusable static addresses that auto-create invoices when payments arrive.

Payouts

Send funds from merchant balances to blockchain addresses.

Webhooks

Webhook overview

Delivery model, 13 event types, and the 5-attempt retry schedule.

Signature verification

HMAC-SHA256 preimage, header format, and working verifier examples.

Event types

All 13 subscribable events with payload field descriptions.

Quickstart

Create your first invoice with the halfin sandbox API in about 5 minutes.

On this page

Get startedResourcesWebhooks