Ethereum API reference: JSON-RPC and Beacon quickstart

The Ethereum API gives developers programmatic access to the canonical EVM blockchain across both of its layers: the execution layer over JSON-RPC for accounts, contracts, logs, and transactions, and the consensus layer over the Beacon Chain REST API for validators, attestations, and finality. Chainstack serves both through a single Ethereum node endpoint.

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Ethereum API at a glance

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What is Ethereum

Ethereum, launched in 2015, is a decentralized, open-source blockchain network that provides a platform for developers to build decentralized applications for diverse purposes. Ethereum runs on a proof-of-stake (PoS) consensus mechanism, and one of its most critical features is smart contract functionality, which lets developers create self-executing programs that automate the enforcement of contractual terms and conditions. Ethereum is the reference implementation of the Ethereum Virtual Machine (EVM), the execution environment that dozens of other chains — Base, BNB Smart Chain, Polygon, Arbitrum, Optimism, and more — adopt for compatibility. Tooling, contract bytecode, and JSON-RPC calls that work against Ethereum carry over to the wider EVM ecosystem with minimal changes. A modern Ethereum node runs two clients that share consensus and produce blocks together:

• Execution layer — processes transactions, runs the EVM, and holds account and contract state. It exposes the JSON-RPC interface that applications use to read state and send transactions.
• Consensus layer — runs proof-of-stake validation through the Beacon Chain, tracking validators, attestations, and finality. It exposes a REST API for validator duties and chain-finality data.

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What is the Ethereum API

The Ethereum API lets developers build decentralized applications, analytics tools, wallets, and indexers. To read data from and send transactions to the Ethereum blockchain, an application connects to an Ethereum node endpoint, then calls the layer it needs:

• The execution layer implements the JSON-RPC specification, a communication protocol that lets you make remote calls and execute them as if they were local. This is where you query balances, blocks, logs, and receipts, call and deploy smart contracts, and submit signed transactions.
• The consensus layer exposes the Beacon Chain REST API for validator state, committees, sync committees, rewards, and finality checkpoints.

A Chainstack Ethereum node serves both, so a single endpoint covers execution-layer JSON-RPC, Beacon Chain queries, and WebSocket subscriptions for real-time data.

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Methods

Chainstack serves 100 Ethereum methods across the execution and consensus layers: For the complete, per-method availability matrix, see Ethereum methods.

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What you can build

With a Chainstack Ethereum endpoint you can:

• Query chain state — balances, blocks, logs, receipts, storage, proofs, and gas — through the standard eth_* JSON-RPC interface, compatible with ethers, viem, and web3.py.
• Deploy and call Solidity contracts with Hardhat, Foundry, Remix, and Ape, using eth_call, eth_estimateGas, and eth_sendRawTransaction.
• Debug and trace transactions with debug_traceTransaction, trace_block, trace_replayTransaction, and the erigon_* namespace on archive nodes.
• Stream real-time data over WebSocket with eth_subscribe for newHeads, logs, newPendingTransactions, and syncing.
• Read consensus-layer state — validators, committees, sync committees, rewards, and finality checkpoints — through the Beacon Chain REST API.
• Index historical state at any block height — balances, contract storage, and traces — against an archive node.

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How to start using the Ethereum API

You need access to an Ethereum node endpoint to use the Ethereum API. Follow these steps to sign up, deploy a node, and find your credentials: Now you are ready to connect to the Ethereum blockchain and use the Ethereum API to build.

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SDKs and tooling

You can call the API directly over HTTP and WebSocket, or use a maintained library:

• JavaScript and TypeScript — ethers.js and viem.
• Python — web3.py.
• .NET — Nethereum.

For smart contract development, point Foundry, Hardhat, Ape, or Scaffold-ETH 2 at your Chainstack endpoint. Point any library or framework at your node URL and add a chain ID. See Ethereum tooling for wallet, IDE, library, and framework setup.

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Networks

Chainstack supports Ethereum mainnet and the Sepolia and Hoodi testnets, with full and archive node modes, WebSocket connections, and debug & trace APIs.

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Frequently asked questions

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What is the Ethereum chain ID?

Ethereum mainnet is chain ID 1. The Chainstack-supported testnets are Sepolia (11155111) and Hoodi (560048). Set the chain ID in your wallet, SDK, or framework config alongside your Chainstack RPC endpoint.

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What is the difference between a full node and an archive node?

A full node keeps recent state — the latest 128 blocks on Ethereum — which covers most live application reads and transaction submission. An archive node retains all historical state from genesis, so you can query balances and contract storage at any past block and run trace_* replays. Chainstack offers both modes on mainnet and Sepolia, and archive on Hoodi.

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Does Ethereum support debug and trace methods?

Yes. Chainstack Ethereum nodes serve the debug_*, trace_*, and erigon_* namespaces — including debug_traceTransaction, trace_block, trace_replayTransaction, and trace_filter — for transaction tracing and smart contract debugging. Debug and trace are available on mainnet, Sepolia, and Hoodi.

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Does Chainstack support WebSocket subscriptions on Ethereum?

Yes. Connect over WebSocket and use eth_subscribe to stream newHeads, logs, newPendingTransactions, and syncing events in real time. Use eth_unsubscribe to cancel a subscription.

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Which SDKs work with the Ethereum API?

Any standard Ethereum library works against a Chainstack endpoint: ethers.js and viem for JavaScript and TypeScript, web3.py for Python, and Nethereum for .NET. For contracts, use Foundry, Hardhat, Ape, or Scaffold-ETH 2. See Ethereum tooling.

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Does Chainstack serve the Beacon Chain (consensus layer) API?

Yes. Chainstack Ethereum nodes expose 31 Beacon Chain REST endpoints alongside execution-layer JSON-RPC, covering validators, committees, sync committees, rewards, finality checkpoints, and the events stream. See Ethereum methods for the full list.

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How are Ethereum requests priced?

Pricing is 1 request unit (RU) per full request and 2 RUs per archive request. For which EVM methods bill as full versus archive, see Request units — EVM methods affected by block age.

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Related Ethereum resources

• Ethereum methods — complete per-method availability reference
• Ethereum tooling — wallets, IDEs, libraries, and frameworks
• Ethereum Trader Nodes with Warp transactions — low-latency transaction propagation
• Ethereum logs tutorial series: logs and filters — query and filter event logs
• Ethereum: how to analyze pending blocks — inspect the mempool and pending state
• Ethereum Dencun: rundown with examples — blobs and the Dencun upgrade
• Debug and trace — tracing method reference and examples
• Subscriptions — WebSocket subscription method reference