klay_getStorageAt

Returns the value from a storage position at a given address.

📘
Supported on Klaytn (mainnet) only.

Parameters

Request

Type	Description
20-byte DATA	Address of the storage.
QUANTITY	Integer of the position in the storage.
QUANTITY \| TAG \| HASH	Integer or hexadecimal block number, or the string `"earliest"`, `"latest"` or `"pending"`, or block hash.

NOTE: In versions earlier than Klaytn v1.7.0, only integer block number, the string "earliest" and "latest" are available.

Result

Type	Description
DATA	The value at this storage position.

API Endpoint

The format of a Klaytn API endpoint is
https://open-platform.nodereal.io/{{apiKey}}/klaytn/

Here is an example:
https://open-platform.nodereal.io/4c0a1c23661a4e26bcbcwed461e34ea9/klaytn/

Example

Calculating the correct position depends on the storage to retrieve. Consider the following contract deployed at 0x295a70b2de5e3953354a6a8344e616ed314d7251 by address 0x391694e7e0b0cce554cb130d723a9d27458f9298.

contract Storage {
    uint pos0;
    mapping(address => uint) pos1;

    function Storage() {
        pos0 = 1234;
        pos1[msg.sender] = 5678;
    }
}

Retrieving the value of pos0 is straight forward:

curl https://open-platform.nodereal.io/{{apiKey}}/klaytn/ \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0", "method": "klay_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x0", "latest"], "id": 1}' 

{"jsonrpc":"2.0","id":1,"result":"0x00000000000000000000000000000000000000000000000000000000000004d2"}

Retrieving an element of the map is harder. The position of an element in the map is calculated with:

keccak(LeftPad32(key, 0), LeftPad32(map position, 0))

This means to retrieve the storage on pos1["0x391694e7e0b0cce554cb130d723a9d27458f9298"] we need to calculate the position with:

keccak(decodeHex("000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"))

The Klaytn console which comes with the klay library can be used to make the calculation

> var key = "000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"
undefined
> klay.sha3(key, {"encoding": "hex"})
"0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9"

Now to fetch the storage:

curl https://open-platform.nodereal.io/{{apiKey}}/klaytn/ \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0", "method": "klay_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "latest"], "id": 1}'

{"jsonrpc":"2.0","id":1,"result":"0x000000000000000000000000000000000000000000000000000000000000162e"}