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

This method takes no parameters. Pass an empty array [].

Response

Type	Description
array	Array of objects, each with `{hash, block, rlp}` — `block` contains the decoded header fields and `rlp` is the raw RLP-encoded block. Returns an empty array if no bad blocks have been seen.

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

Code	Message	Cause
`-32601`	`Method not found`	debug namespace not enabled on the node, or client does not implement this method.

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