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opBNB

opBNB RPC — Free Endpoint & Developer Guide

Jun 20, 2026·4 min read

opBNB is BNB Chain's OP Stack layer-2 for low-cost scaling. This guide shows how to connect to it through MoltNode's free opBNB RPC endpoint — no API key, no signup, just one clean URL.

What is opBNB

opBNB is a layer-2 network that scales BNB Chain by building on the OP Stack, the open optimistic-rollup codebase that also underpins chains like Optimism and Base. It moves execution off the base layer to keep transaction fees very low while settling back to BNB Chain, which makes it well suited to high-volume consumer applications, gaming, and other workloads where cost per transaction matters. Because it is EVM-compatible, the Solidity contracts, developer tooling, and eth_* JSON-RPC methods you already use carry over without modification.

The native gas token on opBNB is BNB, and its EVM chainId is 204. As an OP Stack rollup, opBNB behaves like the rest of the Ethereum-family ecosystem from a developer's point of view: you read balances, estimate gas, query logs, and broadcast transactions using the standard Ethereum JSON-RPC interface. If you have integrated any EVM chain before, opBNB will feel immediately familiar.

opBNB RPC endpoint on MoltNode

MoltNode gives opBNB a single, memorable URL:

https://moltnode.ag/opbnb

That URL is a live opBNB RPC endpoint. There is no API key to manage, no dashboard to sign up for, and CORS is open so you can call it directly 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/opbnb 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 opBNB JSON-RPC. One link works for both people and programs.

Quick test with curl

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

curl -s https://moltnode.ag/opbnb \
  -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 opBNB node URL and you are done. Here is an example with viem:

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

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

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

The same URL drops into ethers, web3.py, wagmi, or any wallet that lets you add a custom network — just use chainId 204, symbol BNB, and the MoltNode URL as the RPC.

Reliability & failover

Behind moltnode.ag/opbnb sits a pool of upstream providers tried in order. Requests are routed to NodeReal, and the gateway is built so that additional upstreams can be added and tried automatically if one is unreachable or returns an error. 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 opBNB 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/opbnb renders a readable page; a POST returns opBNB JSON-RPC. For programmatic discovery, AI agents and scripts can read the full machine-readable catalog at https://moltnode.ag/api/chains to find opBNB'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 204, and start sending eth_* calls with no human in the loop.

Closing

For a free opBNB RPC that just works, point your client at https://moltnode.ag/opbnb. 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.