getLatestBlockhash

Every Solana transaction must reference a recent blockhash so the cluster can reject stale or replayed submissions, and getLatestBlockhash is how you obtain one. It returns the current blockhash together with lastValidBlockHeight — the block height past which a transaction built on that blockhash can no longer land. With Solana's ~400ms slots a blockhash ages quickly, so most senders of SOL or SPL token transactions fetch one immediately before signing. Call it on TheRPC at https://solana.therpc.io/YOUR_API_KEY.

Use cases

• Fetch a fresh blockhash to embed in a transaction message right before you sign and submit a SOL transfer or program call.
• Use the returned lastValidBlockHeight as the hard deadline after which the cluster will drop the transaction.
• Drive a resend loop that keeps retrying sendTransaction until the current block height passes lastValidBlockHeight, then gives up and re-signs with a new blockhash.

Parameters

Response

Example request

1curl https://solana.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5  "jsonrpc": "2.0",
6  "id": 1,
7  "method": "getLatestBlockhash",
8  "params": [
9    {}
10  ]
11}'

Errors & troubleshooting

Common pitfalls

• A blockhash stays usable for only about 150 blocks, so fetch one right before signing rather than caching it far in advance — a stale blockhash makes the transaction unsendable.
• Compare lastValidBlockHeight against the live height from getBlockHeight to know when a pending transaction is dead, so you stop polling getSignatureStatuses for a signature that can never confirm.

Supported networks

• Mainnet
• Devnet

See also

• isBlockhashValid
• getFeeForMessage
• sendTransaction