PDF File Attachments JSON Format Schema

Flow Types

We use Flow type declarations to specify the format of Instant JSON records.

The optional keys are specified as follows:

{ optionalKey?: value; }

To save traffic, these keys should not be included in the record if the value is undefined.


Attachments were added to support syncing annotation attachments across different devices. The keys in attachments are the calculated SHA-256 hashes of the attachment or the pdfObjectId of the attachment. The binary of the attachment is Base64 encoded:

// Example of the Instant JSON schema of an attachments payload with one attachment:
	"attachments": {
		"9e51e601bb7469be642f0b0d60bbb98aeb631353839ab3bc5a25797dbb74622f": {
			"contentType": "image/png"
declare type Attachments = {
  [string]: {
    binary: string

For more information on the annotations Instant JSON schema, please refer to the JSON Format Schema — Annotations guide.