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Optimism

Optimism RPC — Free Endpoint & Developer Guide

Jun 20, 2026·3 min read

Optimism is an Ethereum layer-2 built on the OP Stack and the founding member of the Superchain. This guide shows how to connect to it through MoltNode's free Optimism RPC endpoint — no API key, no signup, just one clean URL.

What is Optimism

Optimism is an EVM-equivalent rollup that settles to Ethereum while moving execution off the base layer to keep fees low and confirmations fast. As an optimistic rollup, it posts transaction data and state to Ethereum and relies on a fraud-proof window for security, inheriting Ethereum's settlement guarantees. Because it is EVM-equivalent, the same Solidity contracts, tooling, and eth_* JSON-RPC methods you already use on Ethereum work here without modification.

The native gas token on Optimism is ETH, and its EVM chainId is 10. Optimism is also the reference implementation of the OP Stack, the shared, open codebase that powers a growing network of interoperable chains known as the Superchain. For developers, that means an Optimism integration is good practice for the broader OP Stack ecosystem.

Optimism RPC endpoint on MoltNode

MoltNode gives Optimism a single, memorable URL:

https://moltnode.ag/optimism

That URL is a live Optimism RPC endpoint. There is no API key to manage, no dashboard to sign up for, and CORS is open so you can call it straight from a browser-based dApp. Send standard JSON-RPC 2.0 requests as an HTTP POST with a JSON body, and you get JSON-RPC responses back.

The same URL is dual-purpose. If you GET https://moltnode.ag/optimism in a browser, you get a human-readable page describing the chain and how to use it. If you POST to it, you get machine-readable Optimism JSON-RPC. One link works for both people and programs.

Quick test with curl

The simplest way to confirm the free Optimism RPC is live is to ask for the latest block number using eth_blockNumber:

curl -s https://moltnode.ag/optimism \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}'

You will get a JSON-RPC response with the current block height as a hex string, for example {"jsonrpc":"2.0","id":1,"result":"0x..."}.

Use it from your code

Because the endpoint speaks plain JSON-RPC, any Ethereum client works. Point it at the Optimism node URL and you are done. Here is an example with viem:

import { createPublicClient, http } from "viem";
import { optimism } from "viem/chains";

const client = createPublicClient({
  chain: optimism,
  transport: http("https://moltnode.ag/optimism"),
});

const block = await client.getBlockNumber();
console.log("Latest Optimism block:", block);

The same URL drops into ethers, web3.py, wagmi, or any wallet that lets you add a custom network — just use chainId 10, symbol ETH, and the MoltNode URL as the RPC.

Reliability & failover

Behind moltnode.ag/optimism sits a small pool of upstream providers tried in order. Requests go first to Alchemy, and if that upstream is unreachable or returns an error, MoltNode automatically fails over to dRPC. You do not see this happen — you just get an answer. The upstream provider keys live server-side and are never exposed to clients, so you get production-grade infrastructure without holding any credentials.

The endpoint has no hard rate limit, but it is a shared resource. Please use it responsibly: cache where you can, avoid tight polling loops, and consider a dedicated provider for heavy production workloads. Treating the Optimism JSON-RPC fairly keeps it fast and free for everyone.

For humans and agents

MoltNode is designed to be discoverable by both developers and autonomous software. A browser GET on https://moltnode.ag/optimism renders a readable page; a POST returns Optimism JSON-RPC. For programmatic discovery, AI agents and scripts can read the full machine-readable catalog at https://moltnode.ag/api/chains to find Optimism's slug, chainId, and endpoint, and there is a plain-text summary at https://moltnode.ag/llms.txt describing how the gateway works. An agent can find the chain, confirm chainId 10, and start sending eth_* calls with no human in the loop.

Closing

For a free Optimism RPC that just works, point your client at https://moltnode.ag/optimism. No key, no signup, open CORS, and automatic failover across upstreams — whether you are building a dApp with viem, scripting with web3.py, adding a custom network to a wallet, or wiring up an AI agent.