slotSubscribe

The Solana slotSubscribe method creates a subscription to receive real-time notifications whenever a validator processes a slot.

Usage Notes

• Must be called via a WebSocket endpoint; HTTP is not supported.
• If the WebSocket connection is closed, subscriptions are automatically cancelled. You must re-subscribe upon reconnection.
• This subscription receives notifications every time a validator processes a slot, which can result in very frequent notifications.
• CU is consumed based on the amount of data subscribed, so it is recommended to use appropriate filtering options to subscribe only to the data you need.

---

1. Request

Parameters

The slot subscription request has the following parameters.

Parameter	Type	Required	Description
id	integer or string	required	Unique identifier for the request. Used by the client to match requests with responses.
jsonrpc	string	required	JSON-RPC protocol version. Always set to "2.0".
method	string	required	Name of the method to execute. Enter "slotSubscribe" here.
params	array	required	No additional parameters are required for slot subscription. Use an empty array.

Example

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "slotSubscribe",
  "params": []
}

---

2. Response

Subscription Response

When the subscription is successfully created, a subscription ID is returned.

{
  "jsonrpc": "2.0",
  "result": 0,
  "id": 1
}

This subscription ID is required when calling the slotUnsubscribe method.

Notifications

Once the subscription is active, the server pushes a notification every time a validator processes a slot.

Notification format:

Field	Type	Description
parent	u64	The parent slot number
root	u64	The current root slot number
slot	u64	The newly set slot value

Slot Notification Example

{
  "jsonrpc": "2.0",
  "method": "slotNotification",
  "params": {
    "result": {
      "parent": 75,
      "root": 44,
      "slot": 76
    },
    "subscription": 0
  }
}

---

3. How to Use

Connect to WebSocket Channel

wscat -c wss://api.mainnet-beta.solana.com

Subscribe to Slots

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "slotSubscribe",
  "params": []
}

Receive Notifications

• Initial response: subscription ID is returned
• Subsequently: a "slotNotification" event is received every time a validator processes a slot

Unsubscribe

There are two ways to unsubscribe:

1. Close the connection: Press Ctrl+C in the terminal window to terminate the WebSocket connection, which automatically cancels all subscriptions.

2. Cancel a specific subscription: Use slotUnsubscribe to cancel only a specific subscription while keeping the connection open.

Unsubscribe request:

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "slotUnsubscribe",
  "params": [0]
}

Response after unsubscribing:

{
  "jsonrpc": "2.0",
  "result": true,
  "id": 2
}