E-Signature API Integration: A Developer's Guide for 2026

Why Integrate E-Signatures via API?

If your application handles contracts, agreements, or any documents that need signing, embedding e-signatures directly into your product creates a seamless experience for your users. Instead of redirecting to a third-party signing page, users stay in your app from start to finish.

Common integration scenarios:

• SaaS platforms — let customers sign terms, contracts, or agreements within your app
• HR systems — automatically generate and send offer letters when candidates are approved
• CRM tools — trigger contract signing directly from deal stages
• Marketplace apps — facilitate agreements between buyers and sellers
• Property management — generate and sign leases within your portal

Getting Started with the SignFlow API

Authentication

All API requests use Bearer token authentication:

`bash curl -X POST https://api.asignflow.com/v2/envelopes \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" `

Generate your API key in Settings → API Keys in your SignFlow dashboard.

Creating an Envelope

An envelope represents a document sent for signature:

`json { "name": "Service Agreement", "documents": [ { "name": "contract.pdf", "base64": "JVBERi0xLjQK..." } ], "recipients": [ { "email": "client@example.com", "name": "Jane Smith", "role": "signer", "order": 1 } ], "fields": [ { "type": "signature", "page": 1, "x": 100, "y": 700, "recipientIndex": 0 } ] } `

Tracking Status

Poll for status or use webhooks:

`bash GET /v2/envelopes/{id}/status `

Response: `json { "status": "completed", "recipients": [ { "email": "client@example.com", "status": "signed", "signedAt": "2026-05-01T14:30:00Z" } ] } `

Webhooks

Register a webhook to receive real-time notifications:

`json { "url": "https://yourapp.com/webhooks/signflow", "events": ["envelope.completed", "envelope.viewed", "recipient.signed"] } `

Embedded Signing

For the smoothest UX, embed the signing experience directly in your app:

`bash POST /v2/envelopes/{id}/signing-url { "recipientEmail": "client@example.com", "returnUrl": "https://yourapp.com/signing-complete" } `

The response includes a URL you can open in an iframe or redirect to.

Best Practices

1. 1Use templates — create templates in the dashboard, then reference them via API for consistent documents
2. 2Implement webhook retries — handle network failures gracefully
3. 3Validate before sending — check that all required fields are placed and recipients are valid
4. 4Use sandbox first — test your integration in sandbox mode before going live
5. 5Store envelope IDs — save the envelope ID in your database for future reference

Rate Limits and Performance

• Standard rate limit: 100 requests per minute
• Bulk operations available for high-volume use cases
• Average response time: under 200ms for most endpoints
• Webhooks delivered within 5 seconds of events

Start Building

SignFlow's API is designed to be simple enough to integrate in a single afternoon. Full documentation, SDKs for popular languages, and a Postman collection are available.

Get your API key and start building →