eth_getBlockTransactionCountByHash

eth_getBlockTransactionCountByHash returns just the number of transactions in the OP Mainnet block identified by a given 32-byte hash, as a hex string. It is a cheap (1 CU) way to gauge how full a block is without downloading the whole block body. OP Mainnet is an OP Stack rollup that pays gas in ETH and seals a block roughly every 2 seconds. Send the block hash to https://optimism.therpc.io/YOUR_API_KEY (chain ID 10, 0xa).

Use cases

• Quickly gauge how full an OP Mainnet block is without downloading the full block body.
• Validate that an indexed block holds the expected transaction count as a sanity check after ingestion.
• Measure OP Mainnet throughput by summing counts across a set of known block hashes over a time window.

Parameters

Response

Example request

1curl https://optimism.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_getBlockTransactionCountByHash",
7    "params": ["0x0000000000000000000000000000000000000000000000000000000000000000"],
8    "id": 1
9  }'

Try it live in the Optimism playground.

Errors & troubleshooting

Common pitfalls

• An unknown hash returns null rather than "0x0" — null-check before passing the result to parseInt(value, 16).
• If you already hold a block number and don't need hash-based certainty against reorgs, use eth_getBlockTransactionCountByNumber instead.

Supported networks

• Mainnet — Chain ID: 10
• Sepolia — Chain ID: 11155420

See also

• eth_getBlockTransactionCountByNumber
• eth_getBlockByHash
• eth_getTransactionByBlockHashAndIndex

1curl https://optimism.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getBlockTransactionCountByHash","params":[""]}'