The Google Docs plugin uses a simple HTTP protocol to communicate with Zotero. The below documentation applies to Zotero 5.0.46 or newer.

Zotero operates a server on port 23119 for Zotero Connector integration. It includes endpoints for integrating with Zotero citing functionality. The integrating plugin or application only needs to be able to send HTTP JSON requests to fully implement the citing protocol.

A single citing integration command is implemented as a series of requests and responses to the HTTP endpoints, constituting a transaction. The integration client begins a transaction by sending a request to http://127.0.0.1:23119/connector/document/execCommand which responds a command to be executed by the client, then subsequent requests with executed command results are made to http://127.0.0.1:23119/connector/document/respond until a transaction is complete.

In order to add a citation to a document, the implementing client sends the following to http://127.0.0.1:23119/connector/document/execCommand:

{
  "command":"addEditCitation",
  "docId":"1ro9AmDxrwbys-xjazJqQG7UlSbBC76CU5xRJ71I8UjE"
}

Zotero then responds by asking for the active document:

{
  "command":"Application.getActiveDocument",
  "arguments":[]
}

The client then sends a response to http://127.0.0.1:23119/connector/document/respond consisting of the the document ID and config options for the implementing client:

{
  "documentID":"1ro9AmDxrwbys-xjazJqQG7UlSbBC76CU5xRJ71I8UjE",
  "outputFormat":"html",
  "supportedNotes":["footnotes"]
}

You can observe the communication between Zotero and Google Docs in the Zotero Connector background page, which is accessed at about:extensions on Chrome by enabling Developer mode and clicking “background page” for Zotero Connector, or at about:debugging on Firefox by clicking “Debug” for Zotero connector. The requests are listed under the Network tab in the developer tools window.

These commands are sent from the word processor to Zotero, and do not receive a response. The command payload always follows this format.

{
  "command":"<Command>",
  "docId":"<Document ID>" // an unique document identifying string
}

If Zotero responds with a 503 HTTP response, it means that another integration transaction is already in progress. If your integration client initiates an integration transaction and fails to complete it by either returning an error or responding to requests until #Document.complete is issued the Zotero integration layer will continuously respond with 503 until it is restarted.

These commands are sent from Zotero to the word processor. They must always receive a response. The command payload is always a JSON-encoded string in the form

{
  "command":"<Command Name>",
  "arguments":[]
}

If the request is successful, the client must send a response with a JSON-encoded payload. This response is often null if the command returns no output, but may also be an array, an integer, a string, or a boolean value depending on the command.

If the request is unsuccessful, the client must send a response with the payload:

{
  "error": "<Error Name>",
  "message": "<Error Message>",
  "stack": "<Optional error stack Object or String>"
}

Zotero will cancel the current operation, log this error, and present it to the user using the Document.displayAlert command if possible. If the subsequent Document.displayAlert command fails, Zotero will present the error using its own dialog box.

Gets information about the client and the currently active document.

N/A

Shows an alert.

(Integer) The index of the button pressed, according to the value of buttons sent as a parameter.

OK = 1

CANCEL = 0
OK = 1

NO = 0
YES = 1

CANCEL = 0
NO = 1
YES = 2

Brings the document to the foreground.

N/A

null

Indicates whether a field can be inserted at the current cursor position.

N/A

(Boolean) Whether a field can be inserted.

Stores a document-specific persistent data string. This data contains the style ID and other user preferences.

null

Retrieves data string set by setDocumentData.

N/A

(String) The document data string.

Indicates whether the cursor is in a given field. If it is, returns information about that field.

Either null, indicating that the cursor isn't in a field, or (Array)

Inserts a new field at the current cursor position.

(Array)

Get all fields present in the document, in document order.

(Array)

Converts all fields in a document to a different fieldType or noteType. Called upon style change from a an in-text to note type or vice-versa

null

Sets parameters to be used to style the bibliography. Numbers are in twips

null

Indicates that the given documentID will no longer be used and associated resources may be freed. NOTE: No further requests to http://127.0.0.1:23119/connector/document/respond should be made after this point

N/A

null

Deletes a field from the document (both its code and its contents).

null

Moves the current cursor position to encompass a field.

null

Removes the field code from a field, leaving it as plain text.

null

Sets the (visible) text of a field.

null

Gets the (visible) text of a field.

(String) The (visible) text

Sets the (hidden, persistent) code of a field.

null

See:

• Dummy Document Client implementation in Zotero tests
• The proper implementation of the HTTP client for our Google Docs plugin