The Zotero streaming API provides push-based notifications via WebSockets for Zotero library changes, allowing for nearly instantaneous updates when data changes in a library or when a user joins or leaves a library.

Note that this API provides library-level notifications of changes. It does not provide updated data directly. API consumers that receive notification of a library change should use their standard sync process to retrieve data, ensuring a single, consistent code path for both manual and automatic syncing.

To avoid missed updates, clients should connect to the streaming API and then, once connected, trigger a standard sync operation to bring themselves up to date with the current version of a library.

var ws = new WebSocket('wss://stream.zotero.org');

Server response:

{"event": "connected", "retry": 10000}

Client message:

{
    "action": "createSubscriptions",
    "subscriptions": [
        {
            "apiKey": "abcdefghijklmn1234567890",
            "topics": [
                "/users/123456",
                "/groups/234567",
                "/groups/345678"
            ]
        },
        {
            "apiKey": "bcdefghijklmn12345678901"
        },
        {
            "topics": [
                "/groups/456789",
                "/groups/567890"
            ]
        }
    ]
}

Server Response:

{
    "event": "subscriptionsCreated",
    "subscriptions": [
        {
            "apiKey": "abcdefghijklmn1234567890",
            "topics": [
                "/users/123456",
                "/groups/234567"
            ]
        },
        {
            "apiKey": "bcdefghijklmn2345678901",
            "topics": [
                "/users/345678"
            ]
        },
        {
            "topics": [
                "/groups/456789"
            ]
        }
    ],
    "errors": [
        {
            "apiKey": "abcdefghijklmn1234567890",
            "topic": "/groups/345678",
            "error": "Topic is not valid for provided API key"
        },
        {
            "topic": "/groups/567890",
            "error": "Topic is not accessible without an API key"
        }
    ]
}

All topic subscriptions — new and existing — for the specified API keys are included in the response. Subscriptions for previously added API keys not in the current request are not included. Subscriptions for public topics can be made without specifying an API key, and the newly added topics will be grouped together in the response.

If a topics property is not provided for an API key, the connection will receive events for all topics available to that key and will automatically track changes to the key's available topics.

Topic subscriptions cannot be removed via createSubscriptions. If subscriptions for a given API key already exist, the provided topics will be merged with the existing ones. If an empty topics array is provided, no changes will be made. If no topics property is provided, the key will be upgraded to automatically track access as described above.

{"event": "topicUpdated", "topic": "/users/123456", "version": 678}
 
{"event": "topicAdded", "apiKey": "abcdefghijklmn1234567890", "topic": "/groups/345678"}
 
{"event": "topicRemoved", "apiKey": "abcdefghijklmn1234567890", "topic": "/groups/234567"}

Client message:

{
    "action": "deleteSubscriptions",
    "subscriptions": [
        {
            "apiKey": "abcdefghijklmn1234567890"
        }
    ]
}

Server response:

{
    "event": "subscriptionsDeleted"
}

Client message:

{
    "action": "deleteSubscriptions",
    "subscriptions": [
        {
            "apiKey": "abcdefghijklmn1234567890",
            "topic": "/users/123456"
        }
    ]
}

Server response:

{
    "event": "subscriptionsDeleted"
}

If a topic is manually removed from a key that is automatically tracking topics, the resulting list of topics will be fixed and the key will no longer receive topicAdded events. It may still receive topicRemoved events if the key loses access to topics.

Client message:

{
    "action": "deleteSubscriptions",
    "subscriptions": [
        {
            "topic": "/users/123456"
        }
    ]
}

Server response:

{
    "event": "subscriptionsDeleted"
}

For API keys without specified topics, the connection will track the key's access and receive events for all topics available to the key.

For example, if the owner of the key joins a group and the key has access to all of the user's groups, the connection will receive a topicAdded event and begin receiving topicUpdated events as data in the group changes.