Signing belongs inside your product.
The API-first e-sign platform for SaaS teams: embed legally binding signatures with one POST, signed webhooks, real SDKs, and a free 500-contract sandbox.
One POST. Signed agreement back.
Send documents, capture consent, receive HMAC-signed webhooks, and store the sealed audit trail — without leaving your product's flow.
curl https://api.ziasign.com/v1/contracts \
-H "Authorization: Bearer $ZIASIGN_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"subject": "Subscription Agreement — Acme",
"documents": [{ "name": "agreement.pdf", "data": "<base64>" }],
"signers": [{ "email": "[email protected]", "name": "Jane Doe" }],
"webhook_url": "https://app.example.com/webhooks/ziasign"
}'What a SaaS team should demand from an e-sign API.
API-first, not API-also
Every platform capability — send, route, remind, seal — is exposed through the same REST API our own apps use. No second-class endpoints.
Signed webhooks
HMAC-signed, retry-safe events for envelope sent, viewed, signed, completed. Idempotent by design so replays never corrupt state.
Tenant isolation & scoped auth
Server-to-server tokens, scoped API keys, OAuth2/JWT patterns, and per-tenant isolation for multi-tenant SaaS.
Compliance you can resell
ESIGN, UETA, eIDAS alignment with SHA-256 hash-chained, tamper-evident audit trails your customers can rely on.
Published, predictable pricing
Free sandbox, production tiers from published rates, pay for contracts shipped — forecastable COGS for your product.
Versioned forever
Stable versions stay stable. Breaking changes carry a 24-month deprecation window, so your roadmap is yours.
SaaS eSignature API, answered.
What is a SaaS eSignature API?
A SaaS eSignature API lets your product create, send, and track legally binding e-signatures programmatically — your users sign inside your app while the API handles identity, consent capture, audit trails, and compliance.
How do I embed e-signatures in my SaaS product?
With ZiaSign: create a contract via one POST to /v1/contracts with your document and signers, receive signing links or embed the flow, then listen for HMAC-signed webhooks for viewed/signed/completed events. Typical integrations ship in an afternoon.
Is there a free eSignature API sandbox?
Yes. The ZiaSign sandbox includes 500 production-shaped contracts, free, with the same API surface as production. No credit card and no sales call required.
Are API-created signatures legally binding?
Yes. Signatures created through the ZiaSign API are designed to satisfy ESIGN, UETA, and eIDAS (AdES) requirements, with court-ready, tamper-evident audit trails secured by a SHA-256 hash chain.
What makes an e-sign platform API-first?
API-first means the API is the product, not an add-on: full capability parity with the UI, real SDKs, signed webhooks, semantic versioning with long deprecation windows, and pricing designed for programmatic volume.
Embed signing this sprint.
500 sandbox contracts, same API shape as production, published pricing when you ship.