# Snapcaster Developers

> The Snapcaster Marketplace partner API 2026-10 connects the backend or POS that supplies a seller's inventory, called a platform, to Snapcaster Marketplace, a Canadian trading card marketplace. Your platform pushes each seller's listings and on-hand stock, Snapcaster handles buyer browse, checkout, payments, and payouts, and Snapcaster sends your platform signed webhooks for each order to fulfill or inventory adjustment to apply. These pages serve the engineers who build and run that integration, from the sandbox to production; each link is the Markdown version of a page, and request and response examples come from the published API contract.

## Get started

- [Start here](https://developers.snapcaster.ca/guide.md): What your platform builds for Snapcaster, and the order to read these docs in.
- [Sandbox quickstart](https://developers.snapcaster.ca/guide/golden-path.md): Push a listing, see it in browse, receive an order, and report fulfillment in the sandbox.
- [Choose your path](https://developers.snapcaster.ca/guide/choose-your-path.md): Decide whether your platform syncs inventory on Path A or fulfills orders on Path B, and which subscription moves your stock.
- [Credentials and onboarding](https://developers.snapcaster.ca/guide/credentials-and-sandbox.md): Onboard your platform, get each seller's marketplace API key and your signing secret in the sandbox and in production, and rotate the secret.

## Shared building blocks

- [Sync a full catalog](https://developers.snapcaster.ca/guide/sync-a-catalog.md): Make a store's Snapcaster listings match a catalog file or export, and retry each write safely.
- [Build a webhook receiver](https://developers.snapcaster.ca/guide/webhook-receiver.md): Receive Snapcaster's signed events, answer each one correctly, and release the hold on sold units.
- [Webhook signing](https://developers.snapcaster.ca/guide/webhook-signing.md): Verify Snapcaster webhook HMAC signatures over the raw request body.

## Path A, inventory sync

- [Keep stock in sync](https://developers.snapcaster.ca/guide/path-a.md): Apply inventory.adjusted events and reconcile stock while sellers ship orders from the Snapcaster dashboard.

## Path B, order fulfillment

- [Receive and ship orders](https://developers.snapcaster.ca/guide/path-b.md): Receive each Snapcaster order, ship it before its deadline, and recover orders your platform missed.
- [Cancel orders and answer requests](https://developers.snapcaster.ca/guide/order-changes.md): Cancel or refund an order, answer buyer requests, and report lines that cannot ship as sold.
- [Handle order updates](https://developers.snapcaster.ca/guide/order-updates.md): Act on each reason Snapcaster sends with order.updated, from address changes to payment refund outcomes.

## Test and launch

- [Sandbox](https://developers.snapcaster.ca/guide/sandbox.md): Look up sandbox guarantees, act as the sandbox buyer, and finish a sandbox seller's setup with the account API.
- [Go live](https://developers.snapcaster.ca/guide/go-live.md): Move your platform and each seller from the sandbox to production, in order, with who acts at each step.

## Concepts

- [Core concepts](https://developers.snapcaster.ca/guide/core-concepts.md): The Marketplace vocabulary shared by listings, browse, and integrations.
- [API versioning](https://developers.snapcaster.ca/guide/api-versioning.md): How Snapcaster sets your platform's API version, how to test another version with a request override, and how to move your pin.

## Reference

- [API reference](https://developers.snapcaster.ca/reference.md): Every operation, webhook and data type in the Snapcaster Marketplace partner contract.
- [Error codes](https://developers.snapcaster.ca/reference/error-codes.md): Marketplace partner error envelopes, meanings, and next actions.
- [Rate limits](https://developers.snapcaster.ca/reference/rate-limits.md): Limit listing batch sizes and handle rate-limit responses.
- [Retries](https://developers.snapcaster.ca/reference/retries.md): Retry each partner API call safely after a timeout, a lost response, a rate limit, or a server error.

## Optional

- [Changelog](https://developers.snapcaster.ca/changelog.md): Marketplace API changes and upgrade instructions by version.