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Documentation Index

Fetch the complete documentation index at: https://docs.sajn.se/llms.txt

Use this file to discover all available pages before exploring further.

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Signer-Fillable Fields

Form fields in sajn can be assigned to a specific signer, requiring them to fill in the value when they sign the document. This is useful when you need information from the signing party that only they can provide, such as their address, personal number, or a date they choose.

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How It Works

By default, form fields in a document are filled by the document creator (you) via the API or dashboard before sending. When you set a signerId on a form field, the field becomes signer-fillable: its value is left empty and the assigned signer sees an input field they must complete during signing. The key properties:
PropertyTypeDescription
signerIdstring (nullable)The ID of the signer who should fill this field. Set to null or omit for creator-filled fields.
requiredbooleanWhether the signer must fill this field before they can sign.

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Prerequisites

  • A document with at least one signer added
  • The signer’s ID (returned when creating the document or adding signers)

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Creating Signer-Fillable Fields

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Step 1: Create a Document with Signers

First, create a document and add signers so you have signer IDs to reference: 
curl -X POST https://app.sajn.se/api/v1/documents \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Rental Agreement",
    "type": "SIGNABLE",
    "signers": [
      {
        "name": "Anna Andersson",
        "email": "anna@example.com",
        "role": "SIGNER",
        "deliveryMethod": "EMAIL",
        "requiredSignature": "BANKID"
      }
    ]
  }'
Response: 
{
  "documentId": "doc_abc123",
  "signers": [
    {
      "signerId": "signer_xyz789",
      "name": "Anna Andersson",
      "email": "anna@example.com"
    }
  ]
}

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Step 2: Add a Form with Signer-Fillable Fields

Add a FORM field where some fields are filled by the signer: 
curl -X POST https://app.sajn.se/api/v1/documents/doc_abc123/fields \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "fields": [{
      "type": "FORM",
      "fieldMeta": {
        "type": "FORM",
        "columns": 1,
        "fields": [
          {
            "id": "field_address",
            "row": 0,
            "column": 0,
            "fieldMeta": {
              "type": "input",
              "label": "Address",
              "placeholder": "Enter your full address",
              "signerId": "signer_xyz789",
              "required": true
            }
          },
          {
            "id": "field_personal_number",
            "row": 1,
            "column": 0,
            "fieldMeta": {
              "type": "input",
              "label": "Personal Number",
              "placeholder": "YYYYMMDD-XXXX",
              "signerId": "signer_xyz789",
              "required": true
            }
          },
          {
            "id": "field_move_in_date",
            "row": 2,
            "column": 0,
            "fieldMeta": {
              "type": "datepicker",
              "label": "Preferred Move-in Date",
              "signerId": "signer_xyz789",
              "required": false
            }
          }
        ]
      }
    }]
  }'
When Anna opens the document to sign, she will see these fields as inputs she needs to fill in. The required fields must be completed before she can sign.

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Step 3: Send for Signing

curl -X POST https://app.sajn.se/api/v1/documents/doc_abc123/send \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{}'

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Mixing Creator and Signer Fields

A common pattern is to pre-fill some fields yourself and leave others for the signer. Only fields with a signerId are editable by the signer — the rest appear as read-only content. 
curl -X POST https://app.sajn.se/api/v1/documents/doc_abc123/fields \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "fields": [{
      "type": "FORM",
      "fieldMeta": {
        "type": "FORM",
        "columns": 2,
        "fields": [
          {
            "id": "field_company",
            "row": 0,
            "column": 0,
            "fieldMeta": {
              "type": "input",
              "label": "Company",
              "value": "RIBBAN AB"
            }
          },
          {
            "id": "field_org_number",
            "row": 0,
            "column": 1,
            "fieldMeta": {
              "type": "input",
              "label": "Org. Number",
              "value": "559254-0321"
            }
          },
          {
            "id": "field_signer_name",
            "row": 1,
            "column": 0,
            "fieldMeta": {
              "type": "input",
              "label": "Your Full Name",
              "signerId": "signer_xyz789",
              "required": true
            }
          },
          {
            "id": "field_signer_email",
            "row": 1,
            "column": 1,
            "fieldMeta": {
              "type": "input",
              "label": "Your Email",
              "placeholder": "name@example.com",
              "signerId": "signer_xyz789",
              "required": true
            }
          }
        ]
      }
    }]
  }'
In this example, “Company” and “Org. Number” are pre-filled and read-only. “Your Full Name” and “Your Email” are filled by the signer.

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Supported Field Types

All form field types support signerId and required:
TypeDescriptionSigner sees
inputSingle-line text inputText field
textMulti-line text areaText area
selectDropdown selectionDropdown with predefined options
datepickerDate selectionDate picker

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Select Field with Signer Assignment

{
  "id": "field_department",
  "row": 0,
  "column": 0,
  "fieldMeta": {
    "type": "select",
    "label": "Department",
    "signerId": "signer_xyz789",
    "required": true,
    "options": [
      { "value": "Engineering" },
      { "value": "Sales" },
      { "value": "Marketing" },
      { "value": "Finance" }
    ]
  }
}

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Multi-Party Signing with Different Fields

When a document has multiple signers, you can assign different fields to each: 
curl -X POST https://app.sajn.se/api/v1/documents \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Partnership Agreement",
    "type": "SIGNABLE",
    "signers": [
      {
        "name": "Partner A",
        "email": "partner-a@example.com",
        "role": "SIGNER",
        "signingOrder": 1,
        "deliveryMethod": "EMAIL",
        "requiredSignature": "DRAWING"
      },
      {
        "name": "Partner B",
        "email": "partner-b@example.com",
        "role": "SIGNER",
        "signingOrder": 2,
        "deliveryMethod": "EMAIL",
        "requiredSignature": "DRAWING"
      }
    ]
  }'
Then assign fields to each signer: 
{
  "fields": [{
    "type": "FORM",
    "fieldMeta": {
      "type": "FORM",
      "columns": 2,
      "fields": [
        {
          "id": "field_partner_a_address",
          "row": 0,
          "column": 0,
          "fieldMeta": {
            "type": "input",
            "label": "Partner A - Address",
            "signerId": "signer_partner_a",
            "required": true
          }
        },
        {
          "id": "field_partner_b_address",
          "row": 0,
          "column": 1,
          "fieldMeta": {
            "type": "input",
            "label": "Partner B - Address",
            "signerId": "signer_partner_b",
            "required": true
          }
        }
      ]
    }
  }]
}
Each signer only sees and fills their own assigned fields. The other party’s fields appear as empty until that signer completes them.

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Updating Signer Assignment

You can update an existing field to assign or unassign a signer using the field update endpoint: 
# Assign a field to a signer
curl -X PATCH https://app.sajn.se/api/v1/documents/doc_abc123/fields/field_456 \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "fieldMeta": {
      "type": "input",
      "signerId": "signer_xyz789",
      "required": true
    }
  }'

# Remove signer assignment (make it creator-filled again)
curl -X PATCH https://app.sajn.se/api/v1/documents/doc_abc123/fields/field_456 \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "fieldMeta": {
      "type": "input",
      "signerId": null,
      "value": "Pre-filled value"
    }
  }'

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Next Steps

Templates and Forms

Pre-fill fields from templates

Multi-Party Signing

Configure signing order and multiple parties

Creating Documents

Full document creation guide

Document Fields API

Complete fields API reference