The logs subscription type emits logs that match a specified topic filter and are included in newly added blocks. To learn more about logs on Ethereum and other EVM chains, check out Understanding Logs: Deep Dive into eth_getLogs.

Supported Networks

Parameters

An object with the following fields:

• address (optional): string] or [array of strings] Singular address or array of addresses. Only logs created from one of these addresses will be emitted.

• topics: an array of topic specifiers (up to 4 topics allowed per address).

  • Each topic specifier is either null, a single string, or an array of strings.
  • For every non null topic, a log will be emitted when activity associated with that topic occurs.

Request

$
// initiate websocket stream first
>
wscat -c wss://eth-mainnet.g.alchemy.com/v2/demo
>
>
// then call subscription 
>
{"jsonrpc":"2.0","id": 1, "method": "eth_subscribe", "params": ["logs", {"address": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48", "topics": ["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"]}]}

Result

1
{
2
    "jsonrpc":"2.0",
3
    "method":"eth_subscription",
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    "params": {
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        "subscription":"0x4a8a4c0517381924f9838102c5a4dcb7",
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        "result":{
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            "address":"0x8320fe7702b96808f7bbc0d4a888ed1468216cfd",
8
            "blockHash":"0x61cdb2a09ab99abf791d474f20c2ea89bf8de2923a2d42bb49944c8c993cbf04",
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            "blockNumber":"0x29e87",
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            "data":"0x00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000003",
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            "logIndex":"0x0",
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            "topics":["0xd78a0cb8bb633d06981248b816e7bd33c2a35a6089241d099fa519e361cab902"],
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            "transactionHash":"0xe044554a0a55067caafd07f8020ab9f2af60bdfe337e395ecd84b4877a3d1ab4",
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            "transactionIndex":"0x0"
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        }
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    }
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}

Below you can find the explanation for individual properties of the response:

• jsonrpc: The jsonrpc property specifies the version of the JSON-RPC protocol that is being used, which in this case is “2.0”.
• method: The method property specifies the method that was called, which in this case is eth_subscription.
• params: The params property contains the parameters of the method call. In this case, it contains a subscription property, which specifies the subscription identifier, and a result property, which contains the result of the subscription.
• result: The result property contains information about a specific transaction on the Ethereum blockchain.
• address: The address property specifies the address from which this log originated.
• blockhash: The blockHash property specifies the hash of the block in which the transaction was included.
• blockNumber: The blockNumber property specifies the number of the block in which the transaction was included. It is encoded as a hexadecimal string.
• data: Contains one or more 32 Bytes non-indexed arguments of the log.
• logIndex: The logIndex property specifies the index or position of the log entry within the block. It is encoded as a hexadecimal string.
• topics: An array of 0 to 4 32 bytes topic hashes of indexed log arguments (up to 4 topics allowed per address).
• transactionHash: The transactionHash property specifies the hash of the transaction.
• transactionIndex: The transactionIndex property specifies the index or position of the transaction within the block. It is encoded as a hexadecimal string.