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Creates a real-time event subscription over a WebSocket connection. Returns a subscription ID; events are pushed as eth_subscription notifications without the client needing to poll.
Flashblocks: On wss://mainnet-preconf.base.org, newHeads emits every ~200ms (once per Flashblock) instead of every ~2 seconds. Three additional subscription types are also available: newFlashblockTransactions, pendingLogs, and newFlashblocks.

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Parameters

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subscriptionType
string
required
The event type to subscribe to.
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filterOptions
object
Optional filter options. Only applicable for the "logs" subscription type.

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Subscription Types

TypeDescriptionNotification payload
newHeadsFires for each new block appended to the chainBlock header object (~200ms on Flashblocks endpoints)
logsFires for each new log matching filter criteriaLog object
newPendingTransactionsFires for each new transaction hash added to the mempoolTransaction hash string

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Returns

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result
string
A hex-encoded subscription ID. All event notifications from this subscription include this ID in params.subscription.
Event notifications arrive as unsolicited JSON-RPC messages: 
{
  "jsonrpc": "2.0",
  "method": "eth_subscription",
  "params": {
    "subscription": "0x1887ec8b9589ccad00000000000532da",
    "result": { ... }
  }
}

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Example

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