Base Block Stream — BlockStream & FlashBlock Subscriptions

BlockRazor offers two complementary block streaming products for the Base network: GetBlockStream for standard low-latency confirmed block data, and GetFlashBlockStream for ultra-low-latency pre-confirmation FlashBlock data sourced directly from the Base sequencer. Both streams are delivered over WebSocket and target applications that need to react to on-chain events as quickly as possible — from arbitrage bots and copy-trading systems to real-time dashboards and order management systems.

FlashBlock is a pre-confirmation block emitted by the Base sequencer before the full block is finalized and published to the network. FlashBlocks arrive earlier than standard confirmed blocks, giving subscribers a significant time advantage for latency-sensitive strategies.

Stream Comparison

Feature	GetBlockStream	GetFlashBlockStream
Data type	Confirmed Base blocks	Pre-confirmation sequencer FlashBlocks
Latency profile	Low	Ultra-low (pre-confirmation)
Helper method	—	`ParseFlashBlock`
Pricing	$300 / stream / month	$250 / stream / month

Connection Details

Property	Value
Protocol	WebSocket (WSS)
Endpoint	`wss://blockstream.blockrazor.io/base?auth=YOUR_AUTH_TOKEN`
Chain	Base (OP Stack / Ethereum L2)

Replace YOUR_AUTH_TOKEN with the API token from your BlockRazor dashboard. Both stream types share the same base endpoint — the method you call after connection determines which stream you receive.

BlockStream
FlashBlockStream

GetBlockStream

GetBlockStream subscribes to fully confirmed Base blocks as they are published. Each message contains the complete block payload including all transactions, the block number, hash, and timestamp. This stream is well-suited for applications that need high confidence in data finality while still maintaining low latency.

Pricing

$300 / stream / month — with multi-month discounts up to 20% for 12-month subscriptions.

Code Example

const WebSocket = require('ws');

const ws = new WebSocket(
  'wss://blockstream.blockrazor.io/base?auth=YOUR_AUTH_TOKEN'
);

ws.on('open', () => {
  console.log('Connected to Base BlockStream');
  // Request the standard confirmed block stream
  ws.send(JSON.stringify({ method: 'GetBlockStream' }));
});

ws.on('message', (data) => {
  const block = JSON.parse(data);
  console.log(
    'New Base block:', block.number,
    'hash:', block.hash,
    'txs:', block.transactions.length,
    'timestamp:', block.timestamp
  );
});

ws.on('error', (err) => console.error('BlockStream error:', err));
ws.on('close', () => console.log('BlockStream connection closed'));

Response Fields

number

string

required

Block number as a hex-encoded string (e.g. "0x7A1B2C"). Decode with parseInt(number, 16) for numeric use.

hash

string

required

32-byte hex block hash uniquely identifying this block on Base.

timestamp

string

required

Unix timestamp of block production, hex-encoded.

transactions

array

required

Array of confirmed transaction objects in this block.

Show Transaction object fields

hash

string

Transaction hash.

from

string

Sender address.

string

Recipient or contract address.

value

string

ETH value in wei, hex-encoded.

gas

string

Gas limit, hex-encoded.

gasPrice

string

Effective gas price in wei, hex-encoded.

data

string

ABI-encoded calldata.

Example Message

{
  "number": "0x7A1B2C",
  "hash": "0xa1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2",
  "timestamp": "0x6613A100",
  "transactions": [
    {
      "hash": "0xb2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3",
      "from": "0xAbCdEf1234567890AbCdEf1234567890AbCdEf12",
      "to": "0x4200000000000000000000000000000000000006",
      "value": "0xDE0B6B3A7640000",
      "gas": "0x5208",
      "gasPrice": "0x77359400",
      "data": "0x"
    }
  ]
}

GetFlashBlockStream

GetFlashBlockStream subscribes to FlashBlocks — pre-confirmation blocks emitted by the Base sequencer before the full block is published to the network. FlashBlocks contain a partial or complete set of transactions that the sequencer has committed to including in the next block, allowing subscribers to act on this information before the rest of the network sees the confirmed block.Use the ParseFlashBlock helper function to decode the raw FlashBlock payload into a structured object that mirrors the standard block format.

Pricing

$250 / stream / month — with multi-month discounts up to 20% for 12-month subscriptions.

FlashBlocks represent the sequencer’s current ordering intent and may differ slightly from the finalized block in edge cases such as sequencer restarts. Always verify critical state transitions against confirmed blocks.

Code Example

const WebSocket = require('ws');

const ws = new WebSocket(
  'wss://blockstream.blockrazor.io/base?auth=YOUR_AUTH_TOKEN'
);

/**
 * ParseFlashBlock decodes a raw FlashBlock message payload
 * into a structured block-like object.
 *
 * @param {string|Buffer} rawData - Raw WebSocket message data
 * @returns {Object} Parsed FlashBlock with number, hash, transactions, timestamp
 */
function ParseFlashBlock(rawData) {
  const payload = JSON.parse(rawData);
  return {
    number: payload.block_number,
    hash: payload.block_hash,
    timestamp: payload.timestamp,
    transactions: payload.txs || [],
    isFlashBlock: true,
    sequencerCommit: payload.sequencer_commit,
  };
}

ws.on('open', () => {
  console.log('Connected to Base FlashBlockStream');
  // Request the FlashBlock pre-confirmation stream
  ws.send(JSON.stringify({ method: 'GetFlashBlockStream' }));
});

ws.on('message', (data) => {
  const flashBlock = ParseFlashBlock(data);
  console.log(
    'FlashBlock received — block:', flashBlock.number,
    'txs:', flashBlock.transactions.length,
    'sequencer commit:', flashBlock.sequencerCommit
  );
});

ws.on('error', (err) => console.error('FlashBlockStream error:', err));
ws.on('close', () => console.log('FlashBlockStream connection closed'));

Compare flashBlock.number against your last confirmed block number to detect new sequencer commitments without waiting for full block finalization. This lets you pipeline transaction analysis and position adjustments ahead of the crowd.

Response Fields (ParseFlashBlock output)

number

string

required

Block number this FlashBlock targets, hex-encoded string (e.g. "0x7A1B2D").

hash

string

required

Sequencer-assigned block hash for this pre-confirmation block.

timestamp

string

required

Unix timestamp at which the sequencer committed this FlashBlock, hex-encoded.

transactions

array

required

Array of transaction objects included in this FlashBlock. Same field schema as the standard BlockStream transaction objects.

isFlashBlock

boolean

required

Always true for FlashBlock messages — useful for distinguishing stream types if you handle both in one handler.

sequencerCommit

string

required

Sequencer signature or commitment identifier for this FlashBlock payload.

Example Parsed FlashBlock

{
  "number": "0x7A1B2D",
  "hash": "0xc3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4",
  "timestamp": "0x6613A102",
  "transactions": [
    {
      "hash": "0xd4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5",
      "from": "0x1234567890AbCdEf1234567890AbCdEf12345678",
      "to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "value": "0x0",
      "gas": "0x493E0",
      "gasPrice": "0x77359400",
      "data": "0xa9059cbb..."
    }
  ],
  "isFlashBlock": true,
  "sequencerCommit": "0xe5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6"
}

Pricing & Discounts

Stream	Monthly Price
GetBlockStream	$300 / stream / month
GetFlashBlockStream	$250 / stream / month

Subscription Period	Discount
1 month	—
3 months	5% off
6 months	10% off
9 months	15% off
12 months	20% off

RPC

Fast

Bundle

Streams

Block Builder

Base Block Stream — BlockStream & FlashBlock Subscriptions

Stream Comparison

Connection Details

GetBlockStream

Pricing

Code Example

Response Fields

Example Message

GetFlashBlockStream

Pricing

Code Example

Response Fields (ParseFlashBlock output)

Example Parsed FlashBlock

Pricing & Discounts

Build docs developers (and LLMs) love

RPC

Fast

Bundle

Streams

Block Builder

Documentation Index

​Stream Comparison

​Connection Details

​GetBlockStream

​Pricing

​Code Example

​Response Fields

​Example Message

​GetFlashBlockStream

​Pricing

​Code Example

​Response Fields (ParseFlashBlock output)

​Example Parsed FlashBlock

​Pricing & Discounts

Build docs developers (and LLMs) love

Stream Comparison

Connection Details

GetBlockStream

Pricing

Code Example

Response Fields

Example Message

GetFlashBlockStream

Pricing

Code Example

Response Fields (ParseFlashBlock output)

Example Parsed FlashBlock

Pricing & Discounts