Get Latest Blockhash

The getLatestBlockhash function retrieves the latest blockhash from the network. Blockhashes are used to ensure transactions are recent and prevent replay attacks.

Usage

const result = await connection.getLatestBlockhash();

Parameters

• commitment: Commitment (optional) - Confirmation level to use (default: “finalized”)
  • "processed" - Processed by current node
  • "confirmed" - Confirmed by supermajority of the cluster
  • "finalized" - Confirmed by supermajority and unlikely to revert

Returns

Returns a Promise<Object> containing:

• blockhash: string - The latest blockhash
• lastValidBlockHeight: bigint - The block height after which this blockhash will no longer be valid
• context: Object - Context information including the slot

Example

// Get the latest blockhash with default commitment
const { blockhash, lastValidBlockHeight } = await connection.getLatestBlockhash();
console.log(`Latest blockhash: ${blockhash}`);
console.log(`Valid until block height: ${lastValidBlockHeight}`);
 
// Get with specific commitment level
const result = await connection.getLatestBlockhash("confirmed");
console.log(`Blockhash (confirmed): ${result.blockhash}`);

Use Cases

• Building transactions that require recent blockhashes
• Checking if a blockhash is still valid
• Monitoring network progression

Notes

• Blockhashes expire after approximately 60 seconds or 150 blocks
• Using “finalized” commitment provides the most reliable blockhash but may be slightly older
• Using “processed” commitment provides the newest blockhash but may not be confirmed yet
• Transactions must be submitted before the lastValidBlockHeight is reached