Skip to main content
With email link authentication, SignatureAPI sends the recipient an email with a direct link. Clicking the link authenticates the recipient and opens their signing session. This is the default authentication method. If you don’t specify a ceremony configuration, SignatureAPI uses email link authentication automatically.

​
When to use

Email link authentication works well when:
  • You want the simplest experience for recipients.
  • Recipients check email to access documents.
  • You don’t need to control the ceremony URL or deliver it through other channels.
  • Your security requirements allow email-based authentication.
You can create an email link ceremony automatically when creating an envelope, or manually using the Create Ceremony endpoint.

​
On envelope creation (automatic)

By default, SignatureAPI creates an email link ceremony and sends the invitation email when you create an envelope.
Default email link ceremony
// POST https://api.signatureapi.com/v1/envelopes
// X-API-Key: key_test_...
// Content-Type: application/json

{
    "title": "Service Agreement",
    "recipients": [
        {
            "type": "signer",
            "key": "client",
            "name": "John Doe",
            "email": "john.doe@example.com"
        }
    ],
    "documents": [ /* ... */ ]
}
To add ceremony options such as a redirect URL, set the ceremony property explicitly.
Email link ceremony with redirect URL
// POST https://api.signatureapi.com/v1/envelopes
// X-API-Key: key_test_...
// Content-Type: application/json

{
    "title": "Service Agreement",
    "recipients": [
        {
            "type": "signer",
            "key": "client",
            "name": "John Doe",
            "email": "john.doe@example.com",
            "ceremony": {
                "authentication": [
                    {
                        "type": "email_link"
                    }
                ],
                "redirect_url": "https://www.example.com/redirect"
            }
        }
    ],
    "documents": [ /* ... */ ]
}

​
Create Ceremony endpoint (manual)

Use the Create Ceremony endpoint to create an email link ceremony after the envelope is created.
Creating a new ceremony automatically revokes any previous ceremony for that recipient. Only the most recent ceremony remains active.
Create email link ceremony
// POST https://api.signatureapi.com/v1/recipients/{recipient_id}/ceremonies
// X-API-Key: key_test_...
// Content-Type: application/json

{
    "authentication": [
        {
            "type": "email_link"
        }
    ]
}

​
Email customization

By default, SignatureAPI derives the email content from the envelope:
  • Subject: envelope.title
  • Message body: envelope.message
  • Language: envelope.language
For example, an envelope with: 
{
  "title": "Dummy Agreement",
  "message": "Please take a moment to review the attached agreement. Once you complete your electronic signature, a signed copy will be sent to your email.\n\nIf you have questions, feel free to reach out."
}
produces an email similar to this:

​
Per-recipient overrides

Use subject_override and message_override on the email_link authentication object to customize the email for a specific recipient.
Per-recipient email customization
// POST https://api.signatureapi.com/v1/envelopes
// X-API-Key: key_test_...
// Content-Type: application/json

{
    "title": "Service Agreement",
    "recipients": [
        {
            "type": "signer",
            "key": "client",
            "name": "John Doe",
            "email": "john.doe@example.com",
            "ceremony": {
                "authentication": [
                    {
                        "type": "email_link",
                        "subject_override": "Action Required: Please sign the Service Agreement",
                        "message_override": "Dear John,\n\nPlease review and sign the attached Service Agreement at your earliest convenience."
                    }
                ]
            }
        }
    ],
    "documents": [ /* ... */ ]
}
message_override supports Markdown formatting: **bold**, *italic*, and \n\n for paragraph breaks. To send invitation emails through your own infrastructure with custom branding, use Custom Authentication to obtain the ceremony URL and deliver it yourself.

​
Audit log

When a recipient clicks the email link, SignatureAPI records the timestamp. The audit log entry looks like this:
12/31/2025 11:59:59 PM
John Doe (#7161cf07) has authenticated using a secure link sent to john⁠@example.com.