debug_getBadBlocks

debug_getBadBlocks reports the blocks a geth-style Ethereum node tried to import but rejected as invalid. On Ethereum mainnet (chain ID 1, native coin ETH), every proposed block must pass execution-layer validation before it joins the canonical chain; anything that fails — a bad state root, an unexecutable transaction, a header that breaks the rules — gets discarded and recorded here. Call it over the TheRPC endpoint at https://ethereum.therpc.io/YOUR_API_KEY. The response is the running list of those rejected blocks observed since the node last started, each carrying its hash, decoded header, and raw RLP bytes for inspection.

Use cases

• Spot consensus violations or malformed blocks that misbehaving peers gossiped onto the network, before they ever reach your application logic.
• Investigate a fork at the head: when a short reorg happens around a 12-second slot, the rejected alternative block shows up here with its full RLP, so you can compare it against the one that won.
• Audit a client's validation path by checking that the blocks it rejected actually violate protocol rules — useful when running geth, erigon, or nethermind side by side.

Parameters

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Response

Example request

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

Try it live in the Ethereum playground.

Errors & troubleshooting

Common pitfalls

• The list lives in memory only. Restart the node and it resets to empty, so this is not a durable audit log.
• On a healthy mainnet node you will almost always get back an empty array. Bad blocks are the exception, not the routine — seeing none is the normal state.
• Not every execution client exposes this method. It is a geth convention; some clients in the Ethereum landscape return -32601 instead of implementing it.

Supported networks

• Mainnet — Chain ID: 1
• Sepolia — Chain ID: 11155111

See also

• debug_traceBlock
• debug_traceBlockByHash
• debug_traceBlockByNumber

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