EIPs/EIPS/eip-695.md

---
eip: 695
title: Create `eth_chainId` method for JSON-RPC
author: Isaac Ardis <isaac.ardis@gmail.com>, Wei Tang (@sorpaas), Fan Torchz (@tcz001)
discussions-to: https://ethereum-magicians.org/t/eip-695-create-eth-chainid-method-for-json-rpc/1845
type: Standards Track
category: Interface
status: Last Call
review-period-end: 2019-07-20
created: 2017-08-21
requires: 155, 1474
---

## Simple Summary

Include `eth_chainId` method in `eth_`-namespaced JSON-RPC methods.

## Abstract

The `eth_chainId` method should return a single STRING result
for an integer value in hexadecimal format, describing the
currently configured `CHAIN_ID` value used for signing replay-protected transactions,
introduced via [EIP-155](./eip-155.md).

## Motivation

Currently although we can use `net_version` RPC call to get the
current network ID, there's no RPC for querying the chain ID. This
makes it impossible to determine the current actual blockchain using
the RPC.

## Specification

### `eth_chainId`

Returns the currently configured chain ID, a value used in replay-protected transaction
signing as introduced by [EIP-155](./eip-155.md).

#### Parameters

None.

#### Returns

`QUANTITY` - integer of the current chain ID.

#### Example

```js
curl -X POST --data '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}'

// Result
{
  "id": 83,
  "jsonrpc": "2.0",
  "result": "0x3d" // 61
}
```

## Rationale

An ETH/ETC client can accidentally connect to an ETC/ETH RPC
endpoint without knowing it unless it tries to sign a transaction or
it fetch a transaction that is known to have signed with a chain
ID. This has since caused trouble for application developers, such as
MetaMask, to add multi-chain support.

## Backwards Compatibility

Not relevant.

## Implementation

- [Parity PR](https://github.com/paritytech/parity/pull/6329)
- [Geth PR](https://github.com/ethereum/go-ethereum/pull/17617)
- [Geth Classic PR](https://github.com/ethereumproject/go-ethereum/pull/336)

## Reference

Return value `QUANTITY` adheres to standard JSON RPC hex value encoding, as documented here: https://github.com/ethereum/wiki/wiki/JSON-RPC#hex-value-encoding.

## Copyright

Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).