eth_getBlockTransactionCountByNumber

eth_getBlockTransactionCountByNumber reports how many transactions a block on OP Mainnet contains, addressed by its height or by a tag such as latest. OP Mainnet is an OP Stack optimistic rollup (Bedrock) that settles to Ethereum L1, pays gas in ETH, and produces a block roughly every two seconds — so this counter ticks far more often than on a slower L1. Send the request to https://optimism.therpc.io/YOUR_API_KEY (chain ID 10, 0xa). The call returns the transaction count for the chosen block as a hex-encoded integer.

Use cases

• Poll the latest block on OP Mainnet to gauge real-time congestion as Velodrome swaps and other Superchain activity fill the sequencer's ~2s blocks.
• Build a per-block fullness time-series to feed fee-estimation heuristics that account for OP Mainnet's L2 execution fee plus the L1 data-availability fee.
• Walk a range of block numbers to flag empty blocks and unusually dense ones when auditing sequencer throughput.

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_getBlockTransactionCountByNumber",
7    "params": ["latest"],
8    "id": 1
9  }'

Try it live in the Optimism playground.

Errors & troubleshooting

Common pitfalls

• The pending tag counts transactions the OP Mainnet sequencer currently holds for the next block, so the value can shift between two calls seconds apart.
• The result is a hex string (e.g. "0x2a"); convert it with parseInt(value, 16) before doing any numeric comparison or arithmetic.

Supported networks

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

See also

• eth_getBlockTransactionCountByHash
• eth_blockNumber
• eth_getBlockByNumber
• eth_getTransactionByBlockNumberAndIndex

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_getBlockTransactionCountByNumber","params":[""]}'