API Reference

Generate PDF, HTML, and image files programmatically by sending JSON data payloads to your activated templates using the ComposeIt REST API.

Authentication

All API requests must include your API key in the custom header:

Header Name	Description
`x-api-key`	Your private organization API key. Manage these in Dashboard > API Keys.

[!CAUTION] Treat your API keys as passwords. Do not expose them in client-side code (e.g. browsers, mobile applications) or public source control repositories.

Render Document

Generate compiled documents by compiling a template definition with dynamic data.

Endpoint: POST /api/export
Content-Type: application/json

Request Parameters

Field	Type	Required	Description
`templateId`	String	Yes	The UUID of the template you wish to render.
`templateVersion`	Number	No	A specific version number to render. Defaults to the active template version.
`formats`	Array	Yes	Output formats to compile. Allowed values: `["pdf", "html", "image", "mjml"]`.
`data`	Object	No	Key-value pairs containing variables referenced inside your template.
`expiresAt`	String	No	ISO 8601 timestamp indicating when the generated download links should expire. (Default: 24 hours).
`imageType`	String	No	Output format of compiled images: `"png"` or `"jpg"`. (Default: `"png"`).
`isTest`	Boolean	No	If `true`, compiles the document with a watermark and avoids counting against subscription usage limits.

Request Example

curl -X POST https://app.composeit.app/api/export \
  -H "Content-Type: application/json" \
  -H "x-api-key: your_live_api_key_here" \
  -d '{
    "templateId": "9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d",
    "formats": ["pdf", "html"],
    "isTest": false,
    "data": {
      "number": "INV-10024",
      "date": "2026-06-26",
      "due_data": "2026-07-26",
      "bill_to": {
        "name": "Acme Corporation",
        "address": "123 Industrial Parkway, Suite A"
      },
      "products": [
        {
          "name": "Premium Plan Subscription",
          "quantity": 1,
          "unit_price": 99.00,
          "total": 99.00
        },
        {
          "name": "Setup & Configuration Service",
          "quantity": 2,
          "unit_price": 50.00,
          "total": 100.00
        }
      ],
      "sub_total": 199.00,
      "tax": 19.90,
      "grand_total": 218.90,
      "notes": "Thank you for partnering with ComposeIt!"
    }
  }'

Response Format

Returns a JSON object mapping each requested format to its compilation result:

{
  "pdf": {
    "url": "https://storage.composeit.website/outputs/9b1deb4d-pdf-output.pdf",
    "sizeBytes": 204550,
    "mimeType": "application/pdf",
    "checksum": "d3b07384d113edec49eaa6238ad5ff00"
  },
  "html": {
    "htmlDocument": "<!DOCTYPE html><html><head><style>...</style></head><body>...</body></html>",
    "checksum": "3b07384d113edec49eaa6238ad5ff001",
    "mimeType": "text/html",
    "url": "",
    "sizeBytes": 14205
  }
}

Error Handling

API responses return appropriate HTTP status codes along with an error message:

400 Bad Request: Missing headers, invalid JSON payload, or unsupported format configuration.
401 Unauthorized: Invalid or missing x-api-key.
404 Not Found: The requested template ID does not exist.
500 Internal Server Error: An unexpected server-side rendering error occurred.

Example Error Payload

{
  "error": "Not found"
}