Polygon chain ID, RPC URL and network config

Last updated: September 23, 2026

Polygon network identifiers

The chain ID is signed into every transaction (EIP-155); the network ID is what net_version reports. They are separate values that happen to match on most chains — see chain ID vs network ID and the chain ID glossary entry.

Polygon RPC URLs

Public-endpoint limits are as each operator publishes them, checked 23 September 2026.

Plans and per-category rate limits: pricing. Network overview: Polygon RPC; method reference: Polygon documentation.

Add Polygon to MetaMask, viem, Hardhat or Foundry

wallet_addEthereumChain (EIP-3085) requires only chainId, as a hex string — 0x89, not 137. The MetaMask block below also fills chainName, nativeCurrency (name, symbol, decimals) and rpcUrls, which a wallet uses to display and reach the network. A wallet cannot send the x-token header, so rpcUrls holds the keyed URL with your API key in the path — paste your key below; the placeholder URL answers 401 until you do.

{
  "method": "wallet_addEthereumChain",
  "params": [{
    "chainId": "0x89",
    "chainName": "Polygon",
    "nativeCurrency": { "name": "POL", "symbol": "POL", "decimals": 18 },
    "rpcUrls": ["https://triport.io/r/<API_KEY>/polygon"]
  }]
}

import { createPublicClient, defineChain, http } from "viem";

export const polygon = defineChain({
  id: 137,
  name: "Polygon",
  nativeCurrency: { name: "POL", symbol: "POL", decimals: 18 },
  rpcUrls: { default: { http: ["https://triport.io/r/<API_KEY>/polygon"], webSocket: ["wss://triport.io/ws/poly/<API_KEY>"] } },
});

export const client = createPublicClient({ chain: polygon, transport: http() });

import { JsonRpcProvider, Network } from "ethers";

const network = Network.from({ name: "polygon", chainId: 137 });
export const provider = new JsonRpcProvider("https://triport.io/r/<API_KEY>/polygon", network, { staticNetwork: network });

// hardhat.config.ts
export default {
  networks: {
    polygon: { url: "https://triport.io/r/<API_KEY>/polygon", chainId: 137 },
  },
};

# foundry.toml
[rpc_endpoints]
polygon = "https://triport.io/r/<API_KEY>/polygon"

import { createConfig, http } from "wagmi";
import { polygon } from "./polygon-chain";

export const config = createConfig({
  chains: [polygon],
  transports: { [polygon.id]: http("https://triport.io/r/<API_KEY>/polygon") },
});

curl https://triport.io/polygon \
  -H "x-token: <API_KEY>" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_chainId","params":[]}'

Keys in URLs vs headers

A keyed URL is the same credential as a header, in a less private place: it lands in shell history, CI logs and screenshots. Use it only where a header is impossible (wallets, hardhat.config, foundry.toml), send x-token from server code, and rotate a key that leaked.

Verify you are on Polygon mainnet

Call eth_chainId first. It must return 0x89 — a client whose configured chain ID disagrees with the reply refuses to connect, which explains most failures when adding a network by hand.

curl https://triport.io/polygon \
  -H "x-token: <API_KEY>" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_chainId","params":[]}'

Sources: the chain's own documentation and the CAIP-2 namespace specs cited in the tables above; EVM chain IDs come from Triport's chain registry and match them.