> ## Documentation Index
> Fetch the complete documentation index at: https://ti-mm-mycompc.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Get the latest finalized Solana blockhash instantly

> Return the most recent finalized blockhash and its last valid block height for client-side transaction construction. Public endpoint, no API key.

Every Solana transaction needs a recent blockhash. This endpoint returns the latest finalized hash plus its `lastValidBlockHeight` so you can build and submit transactions client-side without running your own RPC node. **Free**, no API key required, cheap to call in a loop.

## Why agents use this

* **You need it for every tx.** Any transaction built more than \~90 seconds after the blockhash was fetched will expire. Refresh often.
* **`lastValidBlockHeight` prevents ghost failures.** Compare against current slot to know if your tx window is still open.
* **No RPC infra required.** Devs building agents from scratch can construct + submit transactions with just this and a wallet.
* **Devnet + mainnet from the same endpoint.** Add `?network=devnet` for testing.

## Use cases

* **Client-side tx builder.** Web app or CLI that constructs Solana transactions, fetches blockhash from the gateway, signs locally.
* **Blockhash refresh in a sniper bot.** Cache blockhash for 30 seconds, then refresh. Never submit an expired tx.
* **Tx expiry monitor.** Watch `lastValidBlockHeight` on your queued transactions and re-sign the ones nearing expiry.
* **Onboarding health check.** Users hit blockhash to verify their gateway integration works before committing to a paid plan.
* **Wallet SDK bootstrap.** Custom mobile wallet? Point it here for blockhash so you don't have to bundle an RPC dependency.

## Recipe: fresh-blockhash cache

```typescript blockhash-cache.ts theme={null}
const GATEWAY = "https://solana-pulse-gateway-1021990235790.us-central1.run.app";

let cache: { blockhash: string; lastValidBlockHeight: number; at: number } | null = null;

export async function getFreshBlockhash(maxAgeMs = 30_000) {
  if (cache && Date.now() - cache.at < maxAgeMs) return cache;

  const res = await fetch(`${GATEWAY}/api/solana/blockhash`);
  const data = await res.json();
  cache = { ...data, at: Date.now() };
  return cache;
}
```

<Tip>
  Free endpoint. Pair with [Optimal Fee](/api-reference/solana/optimal-fee) to build fully-configured transactions with two gateway calls and no RPC of your own.
</Tip>