Overview
Flashblocks is a transaction preconfirmation feature on Optimism that provides sub-second feedback (as low as ~200ms) before final block confirmation. Unlike the standard ~2-second block time, Flashblocks lets applications receive early signals about transaction ordering, enabling near-instant UX for time-critical use cases.
Flashblocks is especially useful for:
- Decentralized exchanges and trading platforms – faster order placement feedback
- Onchain games or apps with frequent state updates – smoother real-time gameplay
- Interfaces that benefit from faster feedback – e.g. live dashboards and analytics tools
- Applications that require real-time responsiveness – any latency-sensitive use case
Using Flashblocks with Optimism Endpoints
Flashblocks is currently supported on Optimism Sepolia testnet and can be accessed using your existing QuickNode Optimism endpoint — no additional add-ons are required.
| Network | Flashblocks Availability |
|---|---|
| Optimism Mainnet | ❌ |
| Optimism Sepolia | ✅ |
Supported RPC Methods
Access Flashblocks preconfirmations through your Optimism endpoint by using the pending tag on methods like eth_getBlockByNumber, eth_getBalance, and eth_getTransactionCount. Additionally, fetch Flashblocks related transaction details via methods such as eth_getTransactionReceipt and eth_getTransactionByHash.
| Method | Description |
|---|---|
eth_getBlockByNumber | With "pending", returns the most recent Flashblock |
eth_getTransactionReceipt | Returns receipts for preconfirmed transactions |
eth_getBalance | With "pending", reflects balances from the latest Flashblock |
eth_getTransactionCount | With "pending", returns the updated nonce from Flashblocks |
eth_getTransactionByHash | Returns the transaction with the specified hash |
Resources
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