Subscriptions are a feature of the Ethereum JSON-RPC API that allows developers to receive real-time updates on various blockchain events. Developers can subscribe to specific events of interest, such as new block headers, pending transactions, or contract events.
Note that all subscriptions require a WebSocket connection.
Native EVM subscriptions
Developers can use the following native methods to subscribe to events:
The subscriptions created can be cleared using the following method:
web3.js subscriptions
The web3.js library also offers subscription methods. web3.js subscriptions are the successors of the deprecated web3.eth.filter methods and provide a way for developers to receive real-time updates about events on the blockchain without constantly polling the blockchain for new data.
Subscriptions can be created using one of the following methods:
- subscribe("newBlockHeaders")
- subscribe("pendingTransactions")
- subscribe("logs")
- subscribe("syncing")
The subscriptions created can be cleared using the following method: