> ## Documentation Index > Fetch the complete documentation index at: https://docs.base.org/llms.txt > Use this file to discover all available pages before exploring further. # Overview > Flashblocks-specific RPC methods, WebSocket subscriptions, and the infrastructure stream schema for Base pre-confirmations. All Base public endpoints (`mainnet.base.org` / `sepolia.base.org`) are Flashblocks-enabled, exposing all standard Ethereum JSON-RPC methods plus a set of pre-confirmation-specific additions. These let you read state, simulate transactions, and stream events against sequencer-ordered data up to \~1.8 seconds before a block seals. All [standard Ethereum JSON-RPC methods](/base-chain/api-reference/rpc-overview) support the `"pending"` block tag to resolve against pre-confirmed state instead of the transaction pool. See the [RPC Overview](/base-chain/api-reference/rpc-overview) for endpoint URLs. ## HTTP Methods | Method | Description | | :------------------------------------------------------------------------------------------ | :----------------------------------------------------------- | | [eth\_simulateV1](/base-chain/api-reference/flashblocks-api/eth_simulateV1) | Simulate transaction bundles against pre-confirmed state | | [base\_transactionStatus](/base-chain/api-reference/flashblocks-api/base_transactionStatus) | Check if a transaction has been received by the node mempool | ## WebSocket Subscriptions On a Flashblocks WSS endpoint, `eth_subscribe` with `newHeads` emits a new event approximately every 200ms per Flashblock instead of every 2 seconds. Three additional subscription types are also available that are exclusive to Flashblocks endpoints: | Subscription | Description | | :----------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------- | | [newFlashblockTransactions](/base-chain/api-reference/flashblocks-api/newFlashblockTransactions) | Stream individual transactions as they are pre-confirmed (\~200ms each) | | [pendingLogs](/base-chain/api-reference/flashblocks-api/pendingLogs) | Stream filtered event logs from pre-confirmed transactions | | [newFlashblocks](/base-chain/api-reference/flashblocks-api/newFlashblocks) | Stream full Flashblock payload objects from the sequencer | ## Infrastructure Stream The raw Flashblocks infrastructure stream is the upstream WebSocket feed consumed by Flashblocks-aware RPC nodes. It emits a new message approximately every 200ms as the sequencer pre-confirms transactions. **Applications should not connect directly to the infrastructure stream.** These endpoints are for node operators only. App developers should use the [WebSocket subscription methods](#websocket-subscriptions) above via a Flashblocks-aware RPC provider. | Network | Raw stream URL | | :------ | :-------------------------------------- | | Mainnet | `wss://mainnet.flashblocks.base.org/ws` | | Sepolia | `wss://sepolia.flashblocks.base.org/ws` | ### Flashblock Object The root structure of each infrastructure stream message. Unique identifier for the block being built. Remains consistent across all Flashblocks within a single full block. Flashblock index within the current block. Starts at 0 (system transactions only). User transactions begin at index 1. Typically reaches 9–10 per block, but [may exceed 10](/base-chain/flashblocks/faq#can-the-flashblock-index-exceed-10-is-that-a-bug) during sequencer timing drift. Block header properties. **Only present when `index` is `0`.** See [Base Object](#base-object). Incremental block state changes for this Flashblock. Present in every message. See [Diff Object](#diff-object). Supplemental data. **Unstable — fields may change without notice.** See [Metadata Object](#metadata-object). ### Base Object Contains full block header properties. **Only present in the `index: 0` message** (the first Flashblock of each full block). Hash of the parent block. Address receiving transaction fees (coinbase). Block number in hex. Maximum gas allowed in this block (hex). Unix timestamp of block creation (hex). EIP-1559 base fee per gas (hex). Previous RANDAO value used for on-chain randomness. Arbitrary data field set by the sequencer. Root of the parent beacon block (EIP-4788). ### Diff Object Contains the incremental block state changes for this specific Flashblock. Present in every message. Merkle root of the state trie after applying this Flashblock's transactions. Hash of the partial block at this Flashblock index. Changes with each Flashblock as more transactions are pre-confirmed. Cumulative gas used up to and including this Flashblock (hex). Cumulative blob gas used (EIP-4844, hex). Array of RLP-encoded transactions included in this Flashblock. Validator withdrawals (always empty on Base L2). Merkle root of transaction receipts. Bloom filter for logs in this Flashblock. Merkle root of withdrawals. ### Metadata Object **The `metadata` object is not stable.** Fields may be added, modified, or removed without prior notice. Do not build production dependencies on it — use the [`diff`](#diff-object) object or query finalized block data via standard RPC instead. As of v0.8.0, `new_account_balances` and `receipts` are no longer present in the `metadata` object. `block_number` remains. The `access_list` field is present but always empty. Block number as a decimal integer. ### Receipt Object `metadata.receipts` was removed in v0.8.0. This schema is preserved for reference for older node versions. On v0.8.0+, use [`eth_getTransactionReceipt`](/base-chain/api-reference/ethereum-json-rpc-api/eth_getTransactionReceipt) for polling-based receipt data, or subscribe to [`newFlashblockTransactions`](/base-chain/api-reference/flashblocks-api/newFlashblockTransactions) with `full: true` for a real-time stream of pre-confirmed transaction data including logs. Transaction type: `0x0` Legacy, `0x1` Access List, `0x2` EIP-1559, `0x7e` Deposit (L1→L2). Transaction status: `0x1` for success, `0x0` for failure. Total gas used in the block up to and including this transaction (hex). Array of event logs emitted by the transaction. See [Log Object](#log-object). Bloom filter for the logs in this receipt. Index of the transaction within the block (hex). ### Log Object Contract address that emitted the event. Array of indexed event parameters. Topic 0 is typically the event signature hash. ABI-encoded non-indexed event parameters. Hash of the block containing this log. Block number in hex. Unix timestamp of the block as a hex string. Base L2 extension to the standard Ethereum log schema. Hash of the transaction that emitted this log. Index of the transaction in the block (hex). Log's index position within the block (hex). `true` if the log was removed due to a chain reorg. ### Complete Examples **Index 0** — includes the `base` object (block header): ```json theme={null} { "payload_id": "0x03997352d799c31a", "index": 0, "base": { "parent_hash": "0x9edc29b8b0a1e31d28616e40c16132ad0d58faa8bb952595b557526bdb9a960a", "fee_recipient": "0x4200000000000000000000000000000000000011", "block_number": "0x158a0e9", "gas_limit": "0x3938700", "timestamp": "0x67bf8332", "base_fee_per_gas": "0xfa", "parent_beacon_block_root": "0x15b9e7c8ac4cbe92dafc849ed30a23e91624bbe5cbe199c0ccea3f7de7fc6d49" }, "diff": { "state_root": "0x208fd63edc0681161105f27d03daf9f8c726d8c94e584a3c0696c98291c24333", "block_hash": "0x5c330e55a190f82ea486b61e5b12e27dfb4fb3cecfc5746886ef38ca1281bce8", "gas_used": "0xab3f", "transactions": ["0x7ef8f8a0b4afc0b7ce10e150801bbaf08ac33fecb0f38311793abccb022120d321c6d276..."], "withdrawals": [] }, "metadata": { "block_number": 22585577 } } ``` **Index 1–N (diff only)** — no `base` object: ```json theme={null} { "payload_id": "0x03997352d799c31a", "index": 4, "diff": { "state_root": "0x7a8f45038665072f382730e689f4a1561835c9987fca8942fa95872fb9367eaa", "block_hash": "0x9b32f7a14cbd1efc8c2c5cad5eb718ec9e0c5da92c3ba7080f8d4c49d660c332", "gas_used": "0x1234f", "transactions": ["0x02f90133...", "0x02f90196..."], "withdrawals": [] }, "metadata": { "block_number": 22585577 } } ```