Upload Attachment/External Documents Method

This document contains details for the /api/v1/envelope/attachment endpoint, including how to upload a binary file and the response fields.

Method

Method	POST
URL	/api/v1/envelope/attachment
Authorization	Bearer {token}
Content-Type	application/json
Mailbox UUID header	{uuid}
Body	binary file contents

Use this endpoint to upload a file before you send or fill an envelope. The response returns the uploaded file identifier and filename.

How it works

Upload the file first. Then use the returned attachmentId in the next envelope request.

Use this flow for file fields and external documents. Keep the same mailbox context for the upload and the next envelope request.

Request body

Send the raw file body in binary format. Do not wrap the file in JSON.

Request example

<binary file body>

Response example

{
  "attachmentId": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
  "filename": "contract.pdf",
  "filesize": 0
}

How to use the uploaded file

Use attachmentId as the attachmentUuid value in the envelope XML. Use filename as the field value.

<document id="16c545db-1002-4efb-a4de-b46bc5ed4885">
    <field name="File" attachmentUuid="3fa85f64-5717-4562-b3fc-2c963f66afa6">contract.pdf</field>
</document>

Use the same uploaded file in an external document flow when the template expects an attachment-based document.

Related topics

• Envelope Structure

• Send Envelope

• File Field API