eth_blockNumber

eth_blockNumber returns the height of the most recent block the node has accepted on Ethereum mainnet. Since The Merge a validator proposes one block per 12-second slot, so under normal conditions the number this method reports climbs by one roughly every 12 seconds. It takes no parameters and answers with a single hex integer. Point it at https://ethereum.therpc.io/YOUR_API_KEY (chain ID 1, native coin ETH) and you get the current tip of the canonical chain. It is the lightest call in the whole eth_ namespace.

Use cases

Liveness probe. With no params and a CU cost of 1, it is the cheapest way to confirm your Ethereum endpoint is reachable and not stalled behind the tip.
Anchor a log scan. Read the tip first, then page eth_getLogs backward in fixed windows so you never request a range that runs past the head.
Confirmation loops. Deployment and bridge scripts poll the height and wait until current - txBlock crosses your confirmation threshold before treating a transaction as settled.
Finality gauge. Diff the returned height against the block tagged finalized to see how many slots still sit in the reorg-able window above economic finality.

Parameters

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

Response

Type	Description
string (hex)	Hex-encoded integer block number. Parse with parseInt(value, 16) or BigInt(value).

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

Try it live in the Ethereum playground.

Errors & troubleshooting

Code	Message	Cause
`-32603`	`Internal error`	Node is not reachable or has not yet produced any block.

Common pitfalls

You get back a hex-encoded height such as 0x12d4f1a. Decode it with BigInt(value) or parseInt(value, 16); comparing or adding to the raw string gives garbage.
Two calls a few milliseconds apart often return the same height — blocks only arrive once per ~12s slot, and providers cache the tip. Don't read a flat value as a stalled node.
This number tracks the head, which can still reorg before justification. For money movement read at finalized or safe instead of acting on the raw latest height.

Supported networks

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