> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kraken.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Book
> Subscribe to order book data
WSS
futures.kraken.com/ws/v1
book
The `book` feed returns information about the order book.
***
## Request
`subscribe` or `unsubscribe`
The requested subscription feed. Value: `book`
A list of strings which represent the products that user will receive information upon.
```json Example theme={null}
{
"event": "subscribe",
"feed": "book",
"product_ids": ["PF_XBTUSD"]
}
```
***
## Response Success
One of: `subscribed`, `subscribed_failed`, `unsubscribed`, `unsubscribed_failed`
The result.
The requested subscription feed. Value: `book`
A list of strings which represent the products that user will receive information upon.
```json Example theme={null}
{
"event": "subscribed",
"feed": "book",
"product_ids": ["PF_XBTUSD"]
}
```
***
## Response Snapshot
The subscribed feed.
The subscribed product (referred also as instrument or symbol).
The subscription message sequence number.
Timestamp in milliseconds.
Always null.
The quantity of the entry.
The price of the entry.
The quantity of the entry.
The price of the entry.
```json Example theme={null}
{
"feed": "book_snapshot",
"product_id": "PF_XBTUSD",
"timestamp": 1612269825817,
"seq": 326072249,
"tickSize": null,
"bids": [
{
"price": 34892.5,
"qty": 6385
},
{
"price": 34892,
"qty": 10924
}
],
"asks": [
{
"price": 34911.5,
"qty": 20598
},
{
"price": 34912,
"qty": 2300
}
]
}
```
***
## Response Delta
The subscribed feed.
The subscribed product (referred also as instrument or symbol).
The subscription message sequence number.
Timestamp in milliseconds.
The side of the entry.
The price of the entry.
The quantity of the entry.
```json Example theme={null}
{
"feed": "book",
"product_id": "PF_XBTUSD",
"side": "sell",
"seq": 326094134,
"price": 34981,
"qty": 0,
"timestamp": 1612269953629
}
```
***
## Response Error
Value: `error`
One of: `Invalid product id`, `Invalid feed`, `Json Error`
An error message.
```json Example theme={null}
{
"event": "error",
"message": "Invalid product id"
}
```