JSON-RPC request builder and hex converter

Ethereum JSON-RPC represents quantities as hex strings. Convert between hex and decimal, or pick one of the six read-only methods, fill in the fields and copy a ready JSON-RPC 2.0 body or curl command.

Limits

The builder covers the six read-only methods NodeCache accepts (eth_call, eth_getBalance, eth_getCode, eth_getLogs, eth_blockNumber, eth_chainId) on Ethereum mainnet. Other methods are not offered.
It builds requests only; it does not send them. Replace YOUR_API_KEY in the curl command with your own key.
eth_getLogs here takes a block range and an optional address; topic filters are not included.

Frequently asked questions

Why are block numbers and balances in hex?

JSON-RPC encodes quantities as 0x-prefixed hexadecimal strings. Convert them to decimal to read them.

Does this tool send requests to a node?

No. It only builds the request. Nothing leaves your browser.

Why only six methods?

They are the read-only methods the NodeCache API accepts. Anything else is rejected by that API with an error.