Develop against a real API, safely
Sandbox mode gives you the complete API surface backed by isolated data. Nothing you do in the sandbox affects production, consumes credits, or sends real mail.
Isolated data
Sandbox keys read and write a separate dataset. Your production divisions, projects, and documents are never visible or mutable from the sandbox.
No credits, no postage
Document generation, orders, and mailouts all run end to end but are never billed and never handed to USPS. Test the full lifecycle for free.
Deterministic state
Use meta.state_data to drive webhooks, delivery confirmations, and escalation transitions on demand instead of waiting on real events.
One-call reset
Wipe your sandbox back to a clean slate whenever you need a fresh start — ideal for seeding integration test suites.
Same auth & limits
Sandbox keys use the same Bearer-token scheme and rate-limit headers as production, so your client code needs zero changes to go live.
Full webhooks
Point subscriptions at your local tunnel and exercise the retry/backoff schedule without generating production traffic.
Quickstart
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1
Create an account
Every account has sandbox access from day one. Sign up free.
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2
Generate a sandbox API key
In the dashboard, open API Tokens and create a key with the Sandbox environment selected.
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3
Make your first call
curl https://api.prelienpro.com/api/v1/projects \ -H "Authorization: Bearer sk_sandbox_your_key_here" \ -H "Accept: application/json" -
4
Reset when you need a clean slate
curl -X POST https://api.prelienpro.com/api/v1/sandbox/reset \ -H "Authorization: Bearer sk_sandbox_your_key_here"
Full request and response schemas for every endpoint — including sandbox-only fields — live in the API reference.