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The sajn API is a REST API for electronic signing. You create a document, add the people who sign it, send it, and get a sealed PDF back when everyone has signed. Every signature is backed by an eIDAS seal, and parties can sign with Swedish BankID, other Nordic eIDs, or a drawn or click-to-sign signature.

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What you can build

Contract automation

Generate agreements from templates, fill in values from your system, and send them for signing.

Signing in your product

Embed the signing flow in your own app or send each party a signing URL.

CRM and archive sync

Mirror document status into your CRM and store signed PDFs in your own archive.

Identity checks

Verify a person with BankID through sajn ID before you onboard them.

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Make a request

The base URL for every endpoint is the following:
Authenticate with an API key in the Authorization header, and choose the API version with the Sajn-Version header:
Replace API_KEY with an API key from Inställningar > Utvecklare > API-nycklar in your workspace settings. For more information, see Authentication. Requests and responses are JSON, and timestamps are ISO 8601 in UTC. A sandbox uses the same base URL; the API key decides which environment you reach. For more information, see Sandbox.

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Pin the API version

sajn versions the API by date, in YYYY-MM format. The docs describe 2026-10. We recommend sending Sajn-Version on every request, so your integration keeps working the same way when your organization’s default version changes. For more information, see API versioning.

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Explore the docs

Quickstart

Send your first document and download the signed PDF.

Core concepts

Documents, parties, fields, templates, and how they fit together.

Guides

Task-by-task guides for documents, fields, templates, and embedding.

Webhooks

Get an HTTP request when a document is signed, completed, or rejected.

API fundamentals

Errors, pagination, rate limits, idempotency, and OAuth.

Build with AI

Use these docs and your workspace from an AI assistant.

Upgrading

Move an integration from 2026-09 to 2026-10.

sajn Login

Log your own users in with BankID.

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Tools

  • OpenAPI specification: https://app.sajn.se/api/v1/openapi. Use it to generate a typed client.
  • Postman: import the starter collections.

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Get developer updates

To hear about new endpoints, breaking changes, and deprecations before they ship, turn on developer updates in the sajn app under Inställningar > Utvecklare. Updates go to your account’s email address. For help, contact [email protected].