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debug_traceBlockByNumber - opBNB RPC Method

Trace all transactions in a block by number on opBNB. Analyze gas consumption, debug state transitions, and inspect historical block execution.

Traces all transactions in a block on opBNB identified by its block number or tag. This is the most convenient block-tracing method — pass a block number or "latest" to get full execution traces of every transaction in that block.

Why opBNB? Build on Binance's high-performance L2 processing 100M+ daily transactions with the lowest L2 gas fees with sub-$0.0001 gas fees, 5-10K TPS, sub-second block times via Volta/Maxwell upgrades, and OP Stack architecture.

Archive Node Required

This method requires an archive node with debug APIs enabled. Standard full nodes prune the historical state needed for transaction tracing. Dwellir provides archive node access for opBNB — ensure your plan includes debug namespace support.

When to Use This Method

debug_traceBlockByNumber is essential for GameFi developers, high-frequency dApp builders, and teams requiring BNB Chain integration:

  • Historical Block Analysis — Trace transactions in any past block by number, enabling time-series analysis of opBNB execution patterns
  • Gas Consumption Patterns — Profile gas usage across all transactions in a block to understand network congestion and gas cost trends for fully on-chain games, high-frequency DeFi, and cost-sensitive applications on BNB Chain
  • Debugging State Transitions — Inspect how every transaction in a block changed the global state, useful for verifying protocol upgrades and hard fork behavior
  • Automated Block Scanning — Iterate through block ranges by number to build analytics pipelines, detect anomalies, and index execution traces

Code Examples

Common Use Cases

1. Historical Gas Consumption Analysis

Profile gas usage across a range of blocks on opBNB:

JavaScript
async function analyzeGasOverRange(provider, startBlock, endBlock) {
  const blockStats = [];

  for (let block = startBlock; block <= endBlock; block++) {
    const blockHex = '0x' + block.toString(16);
    const traces = await provider.send('debug_traceBlockByNumber', [
      blockHex,
      { tracer: 'callTracer' }
    ]);

    let totalGas = 0;
    let maxGas = 0;
    let revertCount = 0;

    for (const trace of traces) {
      const gasUsed = parseInt(trace.result.gasUsed, 16);
      totalGas += gasUsed;
      maxGas = Math.max(maxGas, gasUsed);
      if (trace.result.error) revertCount++;
    }

    blockStats.push({
      block,
      txCount: traces.length,
      totalGas,
      avgGas: traces.length > 0 ? Math.round(totalGas / traces.length) : 0,
      maxGas,
      revertCount
    });

    console.log(
      `Block ${block}: ${traces.length} txs, ${totalGas} total gas, ${revertCount} reverts`
    );
  }

  return blockStats;
}

2. Automated Block Scanner for Contract Interactions

Scan blocks for interactions with a specific contract on opBNB:

Python
import requests

def scan_blocks_for_contract(start_block, end_block, target_contract):
    target = target_contract.lower()
    interactions = []

    for block_num in range(start_block, end_block + 1):
        block_hex = hex(block_num)
        response = requests.post('https://api-opbnb-mainnet.n.dwellir.com/YOUR_API_KEY', json={
            'jsonrpc': '2.0',
            'method': 'debug_traceBlockByNumber',
            'params': [block_hex, {'tracer': 'callTracer'}],
            'id': 1
        })
        traces = response.json()['result']

        for trace in traces:
            calls = flatten_calls(trace['result'])
            for call in calls:
                if call.get('to', '').lower() == target:
                    interactions.append({
                        'block': block_num,
                        'tx_hash': trace['txHash'],
                        'call_type': call['type'],
                        'from': call['from'],
                        'input': call['input'][:10],  # function selector
                        'gas_used': int(call.get('gasUsed', '0x0'), 16)
                    })

    print(f'Found {len(interactions)} interactions with {target_contract}')
    for i in interactions:
        print(f'  Block {i["block"]}: {i["tx_hash"]} [{i["call_type"]}] selector={i["input"]}')

    return interactions

def flatten_calls(trace):
    calls = [trace]
    for sub in trace.get('calls', []):
        calls.extend(flatten_calls(sub))
    return calls

3. Debugging State Transitions After Protocol Upgrades

Compare block execution before and after a hard fork or protocol upgrade:

JavaScript
async function compareBlockExecution(provider, forkBlock) {
  const preFork = '0x' + (forkBlock - 1).toString(16);
  const postFork = '0x' + forkBlock.toString(16);

  const [preTraces, postTraces] = await Promise.all([
    provider.send('debug_traceBlockByNumber', [
      preFork,
      { tracer: 'callTracer' }
    ]),
    provider.send('debug_traceBlockByNumber', [
      postFork,
      { tracer: 'callTracer' }
    ])
  ]);

  console.log(`Pre-fork block ${forkBlock - 1}: ${preTraces.length} txs`);
  console.log(`Post-fork block ${forkBlock}: ${postTraces.length} txs`);

  // Analyze opcode-level differences for the first transaction in each
  const [preOpcodes, postOpcodes] = await Promise.all([
    provider.send('debug_traceBlockByNumber', [
      preFork,
      { disableStorage: true, enableReturnData: true }
    ]),
    provider.send('debug_traceBlockByNumber', [
      postFork,
      { disableStorage: true, enableReturnData: true }
    ])
  ]);

  // Check for new opcodes introduced after the fork
  const preOps = new Set();
  const postOps = new Set();

  for (const trace of preOpcodes) {
    for (const log of trace.result.structLogs || []) {
      preOps.add(log.op);
    }
  }

  for (const trace of postOpcodes) {
    for (const log of trace.result.structLogs || []) {
      postOps.add(log.op);
    }
  }

  const newOps = [...postOps].filter(op => !preOps.has(op));
  if (newOps.length > 0) {
    console.log('New opcodes observed after fork:', newOps);
  }
}

Error Handling

Common errors and solutions:

Error CodeDescriptionSolution
-32000Block not foundVerify the block number exists on opBNB — it may be in the future
-32000Missing trie nodeNode is not an archive node or state has been pruned — use an archive endpoint
-32601Method not foundDebug namespace is not enabled on the node
-32603Internal errorBlock may be too large to trace — increase timeout or use disableStorage
-32005Rate limit exceededReduce request frequency or upgrade your plan
-32602Invalid paramsCheck that the block number is a valid hex string or tag
JavaScript
async function safeTraceBlockByNumber(provider, blockNumber, options = {}) {
  const defaultOptions = {
    tracer: 'callTracer',
    timeout: '60s',
    ...options
  };

  try {
    return await provider.send('debug_traceBlockByNumber', [blockNumber, defaultOptions]);
  } catch (error) {
    if (error.code === -32601) {
      throw new Error('debug_traceBlockByNumber not available — ensure archive node with debug API');
    }
    if (error.code === -32000 && error.message?.includes('not found')) {
      throw new Error(`Block ${blockNumber} not found on opBNB`);
    }
    if (error.message?.includes('timeout')) {
      console.warn('Trace timed out — retrying with top-level calls only');
      return await provider.send('debug_traceBlockByNumber', [
        blockNumber,
        { tracer: 'callTracer', tracerConfig: { onlyTopCall: true } }
      ]);
    }
    throw error;
  }
}