Summary
# Optimism RPC: How to Connect to OP Mainnet and Choose the Best Endpoint Optimism is a leading Layer 2 scaling solution for Ethereum that uses Optimistic Rollups to offer low-cost, fast transactions while inheriting Ethereum's security. To interact with OP Mainnet—whether for sending transactions, querying on-chain data, or building dApps—you need an Optimism RPC endpoint. This guide covers everything from the official public RPC URL to third-party providers, how to add Optimism to MetaMask, and how to select the right RPC for production use. Whether you're a developer integrating the OP Stack or a user setting up a wallet, understanding Optimism RPC options—including public, private, and dedicated nodes—is essential for reliable and performant access.
In practice, the useful question is not just whether an endpoint exists. Teams should check supported methods, traffic shape, monitoring, pricing, and the path from testing to production. That turns the page from a definition into a decision tool: it helps you decide what to test first, what belongs in staging, and when a production workload may need stronger isolation or clearer request visibility. If you already know the network you need, open /networks/optimism after using this checklist so you can test the endpoint against your real methods.
Key Takeaways
- Optimism RPC endpoints allow you to interact with OP Mainnet, a Layer 2 Ethereum scaling solution.
- The official public RPC URL (https://mainnet.optimism.io) is rate-limited and does not support WebSocket connections.
- Third-party providers offer private, dedicated, and WebSocket-enabled Optimism RPC endpoints for production use.
- Chain ID for OP Mainnet is 10, and the native currency is ETH.
- Adding Optimism to MetaMask requires the RPC URL, Chain ID, and currency symbol.
- For high-traffic dApps, a dedicated Optimism node provides more predictable resource planning and reliability.
- OnFinality provides Optimism RPC endpoints with scalable infrastructure for developers and enterprises.
What is Optimism RPC?
Optimism RPC (Remote Procedure Call) is the protocol that enables wallets, dApps, and other Web3 applications to communicate with the Optimism blockchain. By sending JSON-RPC requests to an Optimism RPC endpoint, you can read blockchain data, submit transactions, and interact with smart contracts on OP Mainnet.
Optimism is an Ethereum Layer 2 scaling solution that uses Optimistic Rollups to bundle transactions off-chain and submit them to Ethereum, significantly reducing gas costs and increasing throughput. The RPC interface is fully EVM-compatible, meaning you can use the same Ethereum JSON-RPC methods and tools like Web3.js, ethers.js, and viem.
- EVM-compatible: Use standard Ethereum RPC methods (eth_call, eth_sendTransaction, etc.)
- Chain ID: 10 (0xa) for OP Mainnet, 11155420 for OP Sepolia testnet
- Native currency: ETH (same as Ethereum)
- Supports both HTTP and WebSocket transports (depending on provider)
RPC infrastructure decision checklist
Use this checklist to turn the RPC infrastructure question into a practical infrastructure decision instead of a generic provider comparison.
Shortlist providers only after you know which methods, environments, traffic patterns, and support expectations matter to the workload.
- List the exact RPC methods, chains, and environments your app will call.
- Test with the same request pattern your frontend, backend, bot, dashboard, or indexer will use.
- Check whether archive, trace, WebSocket, testnet, analytics, or dedicated-node access is actually required.
- Review pricing, usage visibility, and upgrade paths before moving sustained traffic.
| Criterion | What to check | Why it matters |
|---|---|---|
| Workload fit | Does the provider support the RPC infrastructure methods and environments your product depends on? | A provider that works for a quick read may still be a poor fit for wallets, trading systems, indexers, or release pipelines. |
| Operational visibility | Can the team see request volume, errors, limits, and usage patterns? | Visibility makes it easier to debug failed requests and plan capacity before users feel the problem. |
| Scaling path | Is there a clear path from shared RPC to higher-capacity plans or dedicated nodes? | The right starting point should not force a rebuild when traffic or reliability requirements increase. |
Official Optimism RPC Endpoints
The Optimism Foundation provides public RPC endpoints for OP Mainnet and OP Sepolia. These are free to use but come with rate limits and do not support WebSocket connections. For production applications or WebSocket needs, you should use a third-party RPC provider or run your own node.
Below are the official public endpoints:
| Criterion | What to check | Why it matters |
|---|---|---|
| Network | OP Mainnet | Production Layer 2 network |
| Public RPC URL | https://mainnet.optimism.io | Rate-limited, no WebSocket |
| Chain ID | 10 (0xa) | Required for wallet configuration |
| Currency Symbol | ETH | Used for gas fees |
| Block Explorer | https://explorer.optimism.io | View transactions and contracts |
| WebSocket | Not supported on public endpoint | Use third-party provider for real-time data |
How to Add Optimism to MetaMask
Adding Optimism to MetaMask requires configuring a custom network with the correct RPC URL, Chain ID, and currency symbol. You can do this manually or use one-click tools like ChainList.
- Open MetaMask and click the network dropdown at the top.
- Select 'Add Network' and then 'Add a network manually'.
- Enter the following details:
- - Network Name: OP Mainnet
- - RPC URL: https://mainnet.optimism.io (or a third-party provider URL)
- - Chain ID: 10
- - Currency Symbol: ETH
- - Block Explorer URL: https://explorer.optimism.io
- Click 'Save' to add the network.
Choosing the Best Optimism RPC Provider
While the official public endpoint is fine for testing, production dApps require reliable, high-performance RPC access. Factors to consider when choosing an Optimism RPC provider include availability, latency, rate limits, WebSocket support, and pricing.
Third-party providers offer various tiers: free public endpoints with rate limits, premium shared endpoints with higher throughput, and dedicated nodes for maximum performance. Some providers also offer archive data and trace API support.
- availability and reliability: Look for providers with SLAs and redundant infrastructure.
- Latency: Low-latency endpoints are critical for time-sensitive applications like trading.
- Rate limits: Free tiers often cap requests per second; paid plans offer higher limits.
- WebSocket support: Required for real-time updates (e.g., pending transactions, event logs).
- Archive data: Needed for historical state queries beyond the default 128 blocks.
- Geographic distribution: Global nodes reduce latency for users worldwide.
Optimism RPC with OnFinality
OnFinality offers Optimism RPC endpoints as part of its managed blockchain infrastructure service. Developers can access scalable, reliable RPC APIs for OP Mainnet without managing their own nodes. OnFinality supports both HTTP and WebSocket connections, with options for dedicated nodes for high-traffic applications.
By using OnFinality, you benefit from global node distribution, automatic failover, and flexible pricing. Whether you're building a DeFi protocol, NFT marketplace, or gaming dApp, OnFinality's Optimism RPC endpoints provide the performance and reliability needed for production.
- HTTP and WebSocket endpoints available
- Scalable infrastructure with load balancing
- Dedicated node options for more predictable resource planning
- Easy integration with existing Ethereum tooling
Optimism RPC Troubleshooting Tips
When working with Optimism RPC, you may encounter common issues like rate limiting, connection errors, or incorrect chain configuration. Here are some tips to resolve them.
- Rate limiting: Switch to a provider with higher rate limits or use a dedicated node.
- Connection errors: Verify the RPC URL is correct and the network is reachable.
- WebSocket not connecting: Ensure your provider supports WebSocket and you're using the correct URL.
- Incorrect Chain ID: Double-check that your wallet or dApp is configured with Chain ID 10 for OP Mainnet.
- Transaction failures: Check gas limits and ensure you have sufficient ETH for fees.
Frequently Asked Questions
Frequently Asked Questions
What is the official Optimism RPC URL?
The official public RPC URL for OP Mainnet is https://mainnet.optimism.io. It is rate-limited and does not support WebSocket connections.
Does Optimism RPC support WebSocket?
The official public endpoint does not support WebSocket. For real-time data, use a third-party provider that offers WebSocket endpoints.
What Chain ID does Optimism use?
OP Mainnet uses Chain ID 10 (0xa). The testnet OP Sepolia uses Chain ID 11155420.
Can I use Optimism RPC for free?
Yes, the official public endpoint is free but rate-limited. Many third-party providers also offer free tiers with limited requests per day.
How do I get a dedicated Optimism RPC endpoint?
Providers like OnFinality offer dedicated Optimism nodes for production use. Contact the provider for pricing and setup.
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