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coingecko

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skills/coingecko/SKILL.md

CoinGecko Solana API Development Guide

A comprehensive guide for integrating CoinGecko's on-chain API for Solana. Access real-time token prices, DEX pool data, OHLCV charts, trade history, and market analytics across 1,700+ decentralized exchanges.

Overview

CoinGecko's Solana API provides:

  • Token Prices: Real-time prices by contract address (single or batch)
  • Pool Data: Liquidity pool information, trending pools, top pools
  • OHLCV Charts: Candlestick data for technical analysis
  • Trade History: Recent trades for any pool
  • DEX Discovery: List all DEXes operating on Solana
  • Search: Find pools by token name, symbol, or address
  • Megafilter: Advanced filtering across pools, tokens, and DEXes

Key Features

FeatureDescription
250+ NetworksMulti-chain support including Solana
1,700+ DEXesRaydium, Orca, Jupiter, Meteora, Pump.fun, etc.
15M+ TokensComprehensive token coverage
Real-time DataUpdates every 10-30 seconds
Historical DataOHLCV charts and trade history

Quick Start

Get Your API Key

  1. Demo API (Free): Visit coingecko.com/en/api
  2. Pro API (Paid): Visit coingecko.com/en/api/pricing

Environment Setup

# .env file
COINGECKO_API_KEY=your_api_key_here
COINGECKO_API_TYPE=demo  # or 'pro'

API Configuration

// Configuration for both Demo and Pro APIs
const CONFIG = {
  demo: {
    baseUrl: 'https://api.coingecko.com/api/v3/onchain',
    headerKey: 'x-cg-demo-api-key',
    rateLimit: 30, // calls per minute
  },
  pro: {
    baseUrl: 'https://pro-api.coingecko.com/api/v3/onchain',
    headerKey: 'x-cg-pro-api-key',
    rateLimit: 500, // calls per minute (varies by plan)
  },
};

const apiType = process.env.COINGECKO_API_TYPE || 'demo';
const apiKey = process.env.COINGECKO_API_KEY;

const BASE_URL = CONFIG[apiType].baseUrl;
const HEADER_KEY = CONFIG[apiType].headerKey;

// Solana network identifier
const NETWORK = 'solana';

Basic Token Price Fetch

async function getTokenPrice(tokenAddress: string): Promise<number | null> {
  const url = `${BASE_URL}/simple/networks/${NETWORK}/token_price/${tokenAddress}`;

  const response = await fetch(url, {
    headers: {
      [HEADER_KEY]: apiKey,
      'Accept': 'application/json',
    },
  });

  if (!response.ok) {
    throw new Error(`API error: ${response.status}`);
  }

  const data = await response.json();
  return data.data?.attributes?.token_prices?.[tokenAddress] ?? null;
}

// Usage
const USDC = 'EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v';
const price = await getTokenPrice(USDC);
console.log(`USDC Price: $${price}`);

API Endpoints Reference

Simple Token Price

Get token prices by contract address.

Endpoint: GET /simple/networks/{network}/token_price/{addresses}

Parameters:

ParameterTypeRequiredDescription
networkstringYesNetwork ID (solana)
addressesstringYesComma-separated token addresses (max 30 Demo, 100 Pro)
include_market_capbooleanNoInclude market cap data
include_24hr_volbooleanNoInclude 24h volume
include_24hr_price_changebooleanNoInclude 24h price change %
async function getTokenPrices(addresses: string[]): Promise<Record<string, TokenPriceData>> {
  const addressList = addresses.join(',');
  const url = `${BASE_URL}/simple/networks/${NETWORK}/token_price/${addressList}`;

  const params = new URLSearchParams({
    include_market_cap: 'true',
    include_24hr_vol: 'true',
    include_24hr_price_change: 'true',
  });

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.attributes || {};
}

Token Data by Address

Get detailed token information.

Endpoint: GET /networks/{network}/tokens/{address}

Parameters:

ParameterTypeRequiredDescription
networkstringYesNetwork ID
addressstringYesToken contract address
includestringNoInclude top_pools for liquidity data
interface TokenData {
  address: string;
  name: string;
  symbol: string;
  decimals: number;
  image_url: string;
  price_usd: string;
  fdv_usd: string;
  market_cap_usd: string;
  total_supply: string;
  volume_usd: {
    h24: string;
  };
  price_change_percentage: {
    h24: string;
  };
}

async function getTokenData(address: string): Promise<TokenData> {
  const url = `${BASE_URL}/networks/${NETWORK}/tokens/${address}?include=top_pools`;

  const response = await fetch(url, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.attributes;
}

Multi-Token Data

Batch fetch multiple tokens.

Endpoint: GET /networks/{network}/tokens/multi/{addresses}

async function getMultipleTokens(addresses: string[]): Promise<TokenData[]> {
  const addressList = addresses.join(',');
  const url = `${BASE_URL}/networks/${NETWORK}/tokens/multi/${addressList}`;

  const response = await fetch(url, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => item.attributes) || [];
}

Pool Data by Address

Get detailed pool information.

Endpoint: GET /networks/{network}/pools/{address}

Parameters:

ParameterTypeRequiredDescription
includestringNobase_token, quote_token, dex
include_volume_breakdownbooleanNoVolume breakdown by timeframe
interface PoolData {
  address: string;
  name: string;
  pool_created_at: string;
  base_token_price_usd: string;
  quote_token_price_usd: string;
  base_token_price_native_currency: string;
  fdv_usd: string;
  market_cap_usd: string;
  reserve_in_usd: string;
  price_change_percentage: {
    m5: string;
    h1: string;
    h6: string;
    h24: string;
  };
  transactions: {
    m5: { buys: number; sells: number };
    h1: { buys: number; sells: number };
    h24: { buys: number; sells: number };
  };
  volume_usd: {
    m5: string;
    h1: string;
    h6: string;
    h24: string;
  };
}

async function getPoolData(poolAddress: string): Promise<PoolData> {
  const url = `${BASE_URL}/networks/${NETWORK}/pools/${poolAddress}`;

  const params = new URLSearchParams({
    include: 'base_token,quote_token,dex',
  });

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.attributes;
}

Trending Pools

Get trending pools across all networks or filtered by network.

Endpoint: GET /networks/trending_pools

Parameters:

ParameterTypeDefaultDescription
includestringbase_tokenAttributes to include
pageinteger1Page number
durationstring24h5m, 1h, 6h, 24h
async function getTrendingPools(duration: '5m' | '1h' | '6h' | '24h' = '24h'): Promise<PoolData[]> {
  const url = `${BASE_URL}/networks/trending_pools`;

  const params = new URLSearchParams({
    include: 'base_token,quote_token,dex,network',
    duration,
    page: '1',
  });

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => item.attributes) || [];
}

// Filter for Solana pools
async function getSolanaTrendingPools(): Promise<PoolData[]> {
  const allPools = await getTrendingPools();
  return allPools.filter(pool => pool.network === 'solana');
}

Top Pools on Network

Get top pools by volume on Solana.

Endpoint: GET /networks/{network}/pools

async function getTopPools(page: number = 1): Promise<PoolData[]> {
  const url = `${BASE_URL}/networks/${NETWORK}/pools`;

  const params = new URLSearchParams({
    include: 'base_token,quote_token,dex',
    page: page.toString(),
  });

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => item.attributes) || [];
}

Search Pools

Search for pools by token name, symbol, or address.

Endpoint: GET /search/pools

Parameters:

ParameterTypeDescription
querystringSearch term (name, symbol, address)
networkstringFilter by network
pageintegerPage number
async function searchPools(query: string): Promise<PoolData[]> {
  const url = `${BASE_URL}/search/pools`;

  const params = new URLSearchParams({
    query,
    network: NETWORK,
    include: 'base_token,quote_token,dex',
  });

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => item.attributes) || [];
}

// Search for SOL pools
const solPools = await searchPools('SOL');

Pool OHLCV Chart

Get candlestick data for technical analysis.

Endpoint: GET /networks/{network}/pools/{pool_address}/ohlcv/{timeframe}

Timeframes: day, hour, minute

Parameters:

ParameterTypeDescription
aggregateintegerCandle aggregation (1, 5, 15 for minute; 1, 4, 12 for hour)
before_timestampintegerUnix timestamp for pagination
limitintegerNumber of candles (max 1000)
currencystringusd or token
interface OHLCVData {
  timestamp: number;
  open: number;
  high: number;
  low: number;
  close: number;
  volume: number;
}

async function getPoolOHLCV(
  poolAddress: string,
  timeframe: 'day' | 'hour' | 'minute' = 'hour',
  aggregate: number = 1,
  limit: number = 100
): Promise<OHLCVData[]> {
  const url = `${BASE_URL}/networks/${NETWORK}/pools/${poolAddress}/ohlcv/${timeframe}`;

  const params = new URLSearchParams({
    aggregate: aggregate.toString(),
    limit: limit.toString(),
    currency: 'usd',
  });

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();

  return data.data?.attributes?.ohlcv_list?.map((candle: number[]) => ({
    timestamp: candle[0],
    open: candle[1],
    high: candle[2],
    low: candle[3],
    close: candle[4],
    volume: candle[5],
  })) || [];
}

// Get hourly candles
const hourlyCandles = await getPoolOHLCV(poolAddress, 'hour', 1, 24);

// Get 5-minute candles
const fiveMinCandles = await getPoolOHLCV(poolAddress, 'minute', 5, 100);

Recent Trades

Get recent trades for a pool.

Endpoint: GET /networks/{network}/pools/{pool_address}/trades

interface TradeData {
  block_number: number;
  block_timestamp: string;
  tx_hash: string;
  tx_from_address: string;
  from_token_amount: string;
  to_token_amount: string;
  price_from_in_currency_token: string;
  price_to_in_currency_token: string;
  price_from_in_usd: string;
  price_to_in_usd: string;
  kind: 'buy' | 'sell';
  volume_in_usd: string;
}

async function getRecentTrades(poolAddress: string): Promise<TradeData[]> {
  const url = `${BASE_URL}/networks/${NETWORK}/pools/${poolAddress}/trades`;

  const response = await fetch(url, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => item.attributes) || [];
}

List DEXes on Solana

Get all decentralized exchanges on Solana.

Endpoint: GET /networks/{network}/dexes

interface DexData {
  id: string;
  name: string;
}

async function getSolanaDexes(): Promise<DexData[]> {
  const url = `${BASE_URL}/networks/${NETWORK}/dexes`;

  const response = await fetch(url, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => ({
    id: item.id,
    name: item.attributes.name,
  })) || [];
}

Megafilter (Advanced)

Advanced filtering for pools across networks, DEXes, and tokens.

Endpoint: GET /pools/megafilter

Parameters:

ParameterTypeDescription
networksstringFilter by network(s)
dexesstringFilter by DEX(es)
sortstringSort order (e.g., pool_created_at_desc)
min_reserve_in_usdnumberMinimum liquidity
min_h24_volume_usdnumberMinimum 24h volume
async function getMegafilterPools(options: {
  dexes?: string[];
  minLiquidity?: number;
  minVolume?: number;
  sort?: string;
}): Promise<PoolData[]> {
  const url = `${BASE_URL}/pools/megafilter`;

  const params = new URLSearchParams({
    networks: NETWORK,
    page: '1',
  });

  if (options.dexes) {
    params.set('dexes', options.dexes.join(','));
  }
  if (options.minLiquidity) {
    params.set('min_reserve_in_usd', options.minLiquidity.toString());
  }
  if (options.minVolume) {
    params.set('min_h24_volume_usd', options.minVolume.toString());
  }
  if (options.sort) {
    params.set('sort', options.sort);
  }

  const response = await fetch(`${url}?${params}`, {
    headers: { [HEADER_KEY]: apiKey },
  });

  const data = await response.json();
  return data.data?.map((item: any) => item.attributes) || [];
}

// Get newest Pump.fun pools
const pumpfunPools = await getMegafilterPools({
  dexes: ['pump-fun'],
  sort: 'pool_created_at_desc',
});

// Get high-volume Raydium pools
const raydiumPools = await getMegafilterPools({
  dexes: ['raydium'],
  minVolume: 100000,
  minLiquidity: 50000,
});

Common Solana DEX Identifiers

DEXIDDescription
RaydiumraydiumLeading AMM on Solana
OrcaorcaUser-friendly DEX
JupiterjupiterAggregator with pools
MeteorameteoraDynamic AMM
Pump.funpump-funMemecoin launchpad
OpenBookopenbookOrder book DEX
LifinitylifinityProactive market maker
PhoenixphoenixOn-chain order book

Common Token Addresses

TokenAddress
USDCEPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v
USDTEs9vMFrzaCERmJfrF4H2FYD4KCoNkY11McCe8BenwNYB
SOL (Wrapped)So11111111111111111111111111111111111111112
JUPJUPyiwrYJFskUPiHa7hkeR8VUtAeFoSYbKedZNsDvCN
BONKDezXAZ8z7PnrnRJjz3wXBoRgixCa6xjnB7YaB1pPB263
WIFEKpQGSJtjMFqKZ9KQanSqYXRcF8fBopzLHYxdM65zcjm
PYTHHZ1JovNiVvGrGNiiYvEozEVgZ58xaU3RKwX8eACQBCt3
RAY4k3Dyjzvzp8eMZWUXbBCjEvwSkkk59S5iCNLY3QrkX6R
ORCAorcaEKTdK7LKz57vaAYr9QeNsVEPfiu6QeMU1kektZE

Rate Limits

PlanCalls/MinuteMax Addresses/Request
Demo (Free)3030
Analyst50050
Lite50050
Pro1,000100
EnterpriseCustomCustom

Rate Limit Handling

class RateLimiter {
  private calls: number[] = [];
  private maxCalls: number;
  private windowMs: number = 60000; // 1 minute

  constructor(maxCallsPerMinute: number) {
    this.maxCalls = maxCallsPerMinute;
  }

  async waitForSlot(): Promise<void> {
    const now = Date.now();
    this.calls = this.calls.filter(t => now - t < this.windowMs);

    if (this.calls.length >= this.maxCalls) {
      const oldestCall = this.calls[0];
      const waitTime = this.windowMs - (now - oldestCall);
      await new Promise(resolve => setTimeout(resolve, waitTime));
    }

    this.calls.push(Date.now());
  }
}

// Usage
const rateLimiter = new RateLimiter(30); // Demo API

async function fetchWithRateLimit(url: string): Promise<any> {
  await rateLimiter.waitForSlot();
  const response = await fetch(url, {
    headers: { [HEADER_KEY]: apiKey },
  });
  return response.json();
}

Error Handling

async function safeApiCall<T>(url: string): Promise<T | null> {
  try {
    const response = await fetch(url, {
      headers: { [HEADER_KEY]: apiKey },
    });

    if (response.status === 401) {
      throw new Error('Invalid API key');
    }
    if (response.status === 429) {
      throw new Error('Rate limit exceeded - wait before retrying');
    }
    if (response.status === 404) {
      console.warn('Resource not found');
      return null;
    }
    if (!response.ok) {
      throw new Error(`API error: ${response.status}`);
    }

    return response.json();
  } catch (error) {
    console.error('CoinGecko API error:', error);
    throw error;
  }
}

Common Error Codes

CodeMeaningSolution
401Invalid API keyCheck your API key
429Rate limit exceededWait and retry, or upgrade plan
404Resource not foundCheck address/network ID
500+Server errorRetry with exponential backoff

Best Practices

Security

  • Never commit API keys to git
  • Use environment variables
  • Rotate keys periodically
  • Use separate keys for dev/prod

Performance

  • Batch token requests when possible
  • Cache frequently accessed data
  • Use appropriate timeframes for OHLCV
  • Implement request queuing for rate limits

Data Quality

  • Verify market cap data (may be null if unverified)
  • Check pool liquidity before trusting prices
  • Use multiple timeframes for price analysis
  • Monitor last trade timestamp for activity

Resources

Skill Structure

coingecko/
├── SKILL.md                      # This file
├── resources/
│   ├── api-reference.md          # Complete API endpoint reference
│   ├── network-dex-ids.md        # Solana network and DEX identifiers
│   └── token-addresses.md        # Common Solana token addresses
├── examples/
│   ├── token-prices/
│   │   └── get-token-price.ts    # Token price examples
│   ├── pools/
│   │   └── pool-data.ts          # Pool data examples
│   ├── ohlcv/
│   │   └── ohlcv-charts.ts       # OHLCV chart examples
│   ├── trades/
│   │   └── recent-trades.ts      # Trade history examples
│   └── integration/
│       └── full-client.ts        # Complete client example
├── templates/
│   └── coingecko-client.ts       # Production-ready client template
└── docs/
    └── troubleshooting.md        # Common issues and solutions

optimism

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Author

@0xinit

Stars

53

Repository

0xinit/cryptoskills

skills/optimism/SKILL.md

Optimism

Optimism is an EVM-equivalent Layer 2 using optimistic rollups. Transactions execute on L2 with data posted to Ethereum L1 for security. The OP Stack is the modular framework powering OP Mainnet, Base, Zora, Mode, and the broader Superchain. Smart contracts deploy identically to Ethereum — no custom compiler, no special opcodes.

What You Probably Got Wrong

  • OP Mainnet IS EVM-equivalent, not just EVM-compatible — Your Solidity contracts deploy without modification. No --legacy flag, no custom compiler. forge create and hardhat deploy work identically to Ethereum. If someone tells you to change your Solidity for "OP compatibility", they are wrong.
  • Gas has two components, not one — Every transaction pays L2 execution gas AND an L1 data fee for posting calldata/blobs to Ethereum. If you only estimate L2 gas via eth_estimateGas, your cost estimate will be wrong. The L1 data fee often dominates total cost. Use the GasPriceOracle predeploy at 0x420000000000000000000000000000000000000F.
  • L2→L1 withdrawals take 7 days, not minutes — L1→L2 deposits finalize in ~1-3 minutes. L2→L1 withdrawals require a 7-day challenge period (the "fault proof window"). Users must prove the withdrawal, wait 7 days, then finalize. Three separate transactions on L1. If your UX assumes instant bridging both ways, it is broken.
  • block.number returns the L2 block number, not L1 — On OP Mainnet, block.number is the L2 block number. To get the L1 block number, read the L1Block predeploy at 0x4200000000000000000000000000000000000015. L2 blocks are produced every 2 seconds.
  • msg.sender works normally — there is no tx.origin aliasing on L2 — Cross-domain messages from L1 to L2 alias the sender address (add 0x1111000000000000000000000000000000001111). But for normal L2 transactions, msg.sender behaves exactly like Ethereum. Only worry about aliasing when receiving L1→L2 messages in your contract.
  • Predeploy contracts live at fixed addresses starting with 0x4200... — These are NOT deployed by you. They exist at genesis. L2CrossDomainMessenger, L2StandardBridge, GasPriceOracle, L1Block, and others all live at hardcoded addresses in the 0x4200... range. Do not try to deploy them.
  • The sequencer is centralized but cannot steal funds — The sequencer orders transactions and proposes state roots. If it goes down, you cannot submit new transactions until it recovers (or until permissionless fault proofs allow forced inclusion). But the sequencer cannot forge invalid state — the fault proof system protects withdrawals.
  • EIP-4844 blob data changed the gas model — After the Ecotone upgrade (March 2024), OP Mainnet posts data using EIP-4844 blobs instead of calldata. This reduced L1 data fees by ~10-100x. The GasPriceOracle methods changed. If you are reading pre-Ecotone documentation, the fee formulas are outdated.
  • SuperchainERC20 is not a standard ERC20 — It is a cross-chain token standard for OP Stack chains that enables native interop between Superchain members. Tokens must implement ICrosschainERC20 with crosschainMint and crosschainBurn. Do not assume a regular ERC20 works across chains.

Quick Start

Chain Configuration

import { defineChain } from "viem";
import { optimism, optimismSepolia } from "viem/chains";

// OP Mainnet is built-in
// Chain ID: 10
// RPC: https://mainnet.optimism.io
// Explorer: https://optimistic.etherscan.io

// OP Sepolia is also built-in
// Chain ID: 11155420
// RPC: https://sepolia.optimism.io
// Explorer: https://sepolia-optimistic.etherscan.io

Environment Setup

# .env
PRIVATE_KEY=your_private_key_here
OP_MAINNET_RPC=https://mainnet.optimism.io
OP_SEPOLIA_RPC=https://sepolia.optimism.io
ETHERSCAN_API_KEY=your_optimistic_etherscan_api_key

Viem Client Setup

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

const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);

const publicClient = createPublicClient({
  chain: optimism,
  transport: http(process.env.OP_MAINNET_RPC),
});

const walletClient = createWalletClient({
  account,
  chain: optimism,
  transport: http(process.env.OP_MAINNET_RPC),
});

Chain Configuration

PropertyOP MainnetOP Sepolia
Chain ID1011155420
CurrencyETHETH
RPChttps://mainnet.optimism.iohttps://sepolia.optimism.io
Explorerhttps://optimistic.etherscan.iohttps://sepolia-optimistic.etherscan.io
Block time2 seconds2 seconds
Withdrawal period7 days~12 seconds (testnet)

Alternative RPCs

ProviderEndpoint
Alchemyhttps://opt-mainnet.g.alchemy.com/v2/<KEY>
Infurahttps://optimism-mainnet.infura.io/v3/<KEY>
QuickNodeCustom endpoint per project
Conduithttps://rpc.optimism.io

Deployment

OP Mainnet is EVM-equivalent. Deploy exactly as you would to Ethereum.

Foundry

# Deploy to OP Mainnet
forge create src/MyContract.sol:MyContract \
  --rpc-url $OP_MAINNET_RPC \
  --private-key $PRIVATE_KEY \
  --broadcast

# Deploy with constructor args
forge create src/MyToken.sol:MyToken \
  --rpc-url $OP_MAINNET_RPC \
  --private-key $PRIVATE_KEY \
  --constructor-args "MyToken" "MTK" 18 \
  --broadcast

# Deploy via script
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $OP_MAINNET_RPC \
  --private-key $PRIVATE_KEY \
  --broadcast \
  --verify \
  --etherscan-api-key $ETHERSCAN_API_KEY

Hardhat

// hardhat.config.ts
import { HardhatUserConfig } from "hardhat/config";
import "@nomicfoundation/hardhat-toolbox";

const config: HardhatUserConfig = {
  solidity: "0.8.24",
  networks: {
    optimism: {
      url: process.env.OP_MAINNET_RPC || "https://mainnet.optimism.io",
      accounts: [process.env.PRIVATE_KEY!],
    },
    optimismSepolia: {
      url: process.env.OP_SEPOLIA_RPC || "https://sepolia.optimism.io",
      accounts: [process.env.PRIVATE_KEY!],
    },
  },
  etherscan: {
    apiKey: {
      optimisticEthereum: process.env.ETHERSCAN_API_KEY!,
      optimisticSepolia: process.env.ETHERSCAN_API_KEY!,
    },
  },
};

export default config;

npx hardhat run scripts/deploy.ts --network optimism

Verification

Foundry

# Verify after deployment
forge verify-contract <DEPLOYED_ADDRESS> src/MyContract.sol:MyContract \
  --chain-id 10 \
  --etherscan-api-key $ETHERSCAN_API_KEY

# Verify with constructor args
forge verify-contract <DEPLOYED_ADDRESS> src/MyToken.sol:MyToken \
  --chain-id 10 \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(string,string,uint8)" "MyToken" "MTK" 18)

Hardhat

npx hardhat verify --network optimism <DEPLOYED_ADDRESS> "MyToken" "MTK" 18

Blockscout

OP Mainnet also has a Blockscout explorer at https://optimism.blockscout.com. Verification works via the standard Blockscout API — set the verifier URL in Foundry:

forge verify-contract <DEPLOYED_ADDRESS> src/MyContract.sol:MyContract \
  --verifier blockscout \
  --verifier-url https://optimism.blockscout.com/api/

Cross-Chain Messaging

The CrossDomainMessenger is the canonical way to send arbitrary messages between L1 and L2. It handles replay protection, sender authentication, and gas forwarding.

Architecture

L1 → L2 (Deposits):
  User → L1CrossDomainMessenger → OptimismPortal → L2CrossDomainMessenger → Target

L2 → L1 (Withdrawals):
  User → L2CrossDomainMessenger → L2ToL1MessagePasser → [7 day wait] → OptimismPortal → L1CrossDomainMessenger → Target

L1 → L2 Message (Deposit)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface IL1CrossDomainMessenger {
    function sendMessage(
        address _target,
        bytes calldata _message,
        uint32 _minGasLimit
    ) external payable;
}

contract L1Sender {
    IL1CrossDomainMessenger public immutable messenger;

    constructor(address _messenger) {
        messenger = IL1CrossDomainMessenger(_messenger);
    }

    /// @notice Send a message from L1 to a contract on L2.
    /// @param l2Target The L2 contract address to call.
    /// @param message The calldata to send to the L2 target.
    /// @param minGasLimit Minimum gas for L2 execution. Overestimate — unused gas is NOT refunded to L1.
    function sendToL2(
        address l2Target,
        bytes calldata message,
        uint32 minGasLimit
    ) external payable {
        messenger.sendMessage{value: msg.value}(l2Target, message, minGasLimit);
    }
}

L2 → L1 Message (Withdrawal)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface IL2CrossDomainMessenger {
    function sendMessage(
        address _target,
        bytes calldata _message,
        uint32 _minGasLimit
    ) external payable;

    function xDomainMessageSender() external view returns (address);
}

contract L2Sender {
    /// @dev L2CrossDomainMessenger predeploy address — same on all OP Stack chains
    IL2CrossDomainMessenger public constant MESSENGER =
        IL2CrossDomainMessenger(0x4200000000000000000000000000000000000007);

    function sendToL1(
        address l1Target,
        bytes calldata message,
        uint32 minGasLimit
    ) external payable {
        MESSENGER.sendMessage{value: msg.value}(l1Target, message, minGasLimit);
    }
}

Receiving Cross-Chain Messages

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface ICrossDomainMessenger {
    function xDomainMessageSender() external view returns (address);
}

contract L2Receiver {
    ICrossDomainMessenger public constant MESSENGER =
        ICrossDomainMessenger(0x4200000000000000000000000000000000000007);

    address public immutable l1Sender;

    constructor(address _l1Sender) {
        l1Sender = _l1Sender;
    }

    modifier onlyFromL1Sender() {
        require(
            msg.sender == address(MESSENGER) &&
            MESSENGER.xDomainMessageSender() == l1Sender,
            "Not authorized L1 sender"
        );
        _;
    }

    function handleMessage(uint256 value) external onlyFromL1Sender {
        // Process the cross-chain message
    }
}

Sender Aliasing

When an L1 contract sends a message to L2, the apparent msg.sender on L2 is the aliased address:

l2Sender = l1ContractAddress + 0x1111000000000000000000000000000000001111

The CrossDomainMessenger handles un-aliasing internally. If you bypass the messenger and send directly via OptimismPortal, you must account for aliasing yourself.

Predeploy Contracts

These contracts exist at genesis on every OP Stack chain. Do not deploy them — they are already there.

ContractAddressPurpose
L2ToL1MessagePasser0x4200000000000000000000000000000000000016Initiates L2→L1 withdrawals
L2CrossDomainMessenger0x4200000000000000000000000000000000000007Sends/receives cross-chain messages
L2StandardBridge0x4200000000000000000000000000000000000010Bridges ETH and ERC20 tokens
L2ERC721Bridge0x4200000000000000000000000000000000000014Bridges ERC721 tokens
GasPriceOracle0x420000000000000000000000000000000000000FL1 data fee calculation
L1Block0x4200000000000000000000000000000000000015Exposes L1 block info on L2
WETH90x4200000000000000000000000000000000000006Wrapped ETH
L1BlockNumber0x4200000000000000000000000000000000000013L1 block number (deprecated, use L1Block)
SequencerFeeVault0x4200000000000000000000000000000000000011Collects sequencer fees
BaseFeeVault0x4200000000000000000000000000000000000019Collects base fees
L1FeeVault0x420000000000000000000000000000000000001ACollects L1 data fees
GovernanceToken0x4200000000000000000000000000000000000042OP token on L2

Reading L1 Block Info

interface IL1Block {
    function number() external view returns (uint64);
    function timestamp() external view returns (uint64);
    function basefee() external view returns (uint256);
    function hash() external view returns (bytes32);
    function batcherHash() external view returns (bytes32);
    function l1FeeOverhead() external view returns (uint256);
    function l1FeeScalar() external view returns (uint256);
    function blobBaseFee() external view returns (uint256);
    function baseFeeScalar() external view returns (uint32);
    function blobBaseFeeScalar() external view returns (uint32);
}

// Usage
IL1Block constant L1_BLOCK = IL1Block(0x4200000000000000000000000000000000000015);
uint64 l1BlockNumber = L1_BLOCK.number();
uint256 l1BaseFee = L1_BLOCK.basefee();

Gas Model

Every OP Mainnet transaction pays two fees:

  1. L2 execution fee — Standard EVM gas, priced by L2 basefee + optional priority fee. Calculated identically to Ethereum.
  2. L1 data fee — Cost of posting the transaction's data to Ethereum L1 as calldata or blob data. This is the OP-specific component.

Post-Ecotone Formula (Current)

After the Ecotone upgrade (March 2024), L1 data fee uses a two-component formula based on calldata gas and blob gas:

l1DataFee = (l1BaseFeeScalar * l1BaseFee * 16 + l1BlobBaseFeeScalar * l1BlobBaseFee) * compressedTxSize / 1e6
  • l1BaseFee — Ethereum L1 base fee (from L1Block predeploy)
  • l1BlobBaseFee — EIP-4844 blob base fee (from L1Block predeploy)
  • l1BaseFeeScalar — System-configured scalar for calldata cost component
  • l1BlobBaseFeeScalar — System-configured scalar for blob cost component
  • compressedTxSize — Estimated compressed size of the signed transaction

GasPriceOracle

interface IGasPriceOracle {
    /// @notice Estimate L1 data fee for raw signed transaction bytes
    function getL1Fee(bytes memory _data) external view returns (uint256);

    /// @notice Get current L1 base fee (read from L1Block)
    function l1BaseFee() external view returns (uint256);

    /// @notice Ecotone: get blob base fee
    function blobBaseFee() external view returns (uint256);

    /// @notice Ecotone: get base fee scalar
    function baseFeeScalar() external view returns (uint32);

    /// @notice Ecotone: get blob base fee scalar
    function blobBaseFeeScalar() external view returns (uint32);

    /// @notice Check if Ecotone is active
    function isEcotone() external view returns (bool);

    /// @notice Check if Fjord is active
    function isFjord() external view returns (bool);

    /// @notice Fjord: estimate compressed size using FastLZ
    function getL1GasUsed(bytes memory _data) external view returns (uint256);
}

IGasPriceOracle constant GAS_ORACLE =
    IGasPriceOracle(0x420000000000000000000000000000000000000F);

Estimating Total Cost in TypeScript

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

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

const GAS_ORACLE = "0x420000000000000000000000000000000000000F" as const;

const gasPriceOracleAbi = parseAbi([
  "function getL1Fee(bytes memory _data) external view returns (uint256)",
  "function l1BaseFee() external view returns (uint256)",
  "function blobBaseFee() external view returns (uint256)",
  "function baseFeeScalar() external view returns (uint32)",
  "function blobBaseFeeScalar() external view returns (uint32)",
]);

async function estimateTotalCost(serializedTx: `0x${string}`) {
  const [l2GasEstimate, gasPrice, l1DataFee] = await Promise.all([
    client.estimateGas({ data: serializedTx }),
    client.getGasPrice(),
    client.readContract({
      address: GAS_ORACLE,
      abi: gasPriceOracleAbi,
      functionName: "getL1Fee",
      args: [serializedTx],
    }),
  ]);

  const l2ExecutionFee = l2GasEstimate * gasPrice;
  const totalFee = l2ExecutionFee + l1DataFee;

  return {
    l2ExecutionFee,
    l1DataFee,
    totalFee,
  };
}

Gas Optimization Tips

  • Minimize calldata: the L1 data fee scales with transaction data size. Fewer bytes = lower L1 fee.
  • Use 0 bytes when possible: zero bytes cost 4 gas in calldata vs 16 gas for non-zero bytes.
  • Batch operations: one large transaction costs less in L1 data fee overhead than many small ones.
  • After Ecotone, blob pricing makes L1 data fees much cheaper and more stable than pre-Ecotone calldata pricing.

Standard Bridge

The Standard Bridge enables ETH and ERC20 transfers between L1 and L2. It is a pair of contracts: L1StandardBridge on Ethereum and L2StandardBridge (predeploy) on OP Mainnet.

Bridge ETH: L1 → L2

interface IL1StandardBridge {
    /// @notice Bridge ETH to L2. Appears at recipient address on L2 after ~1-3 min.
    function depositETH(uint32 _minGasLimit, bytes calldata _extraData) external payable;

    /// @notice Bridge ETH to a different address on L2.
    function depositETHTo(
        address _to,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;
}

Bridge ETH: L2 → L1

interface IL2StandardBridge {
    /// @notice Initiate ETH withdrawal to L1. Requires prove + finalize after 7 days.
    function withdraw(
        address _l2Token,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;
}

// Withdraw ETH from L2 to L1
// _l2Token = 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000 (legacy ETH representation)
// Send ETH as msg.value, set _amount to the same value

Bridge ERC20: L1 → L2

interface IL1StandardBridge {
    /// @notice Bridge ERC20 to L2. Token must have a corresponding L2 representation.
    function depositERC20(
        address _l1Token,
        address _l2Token,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external;

    function depositERC20To(
        address _l1Token,
        address _l2Token,
        uint256 _amount,
        address _to,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external;
}

Bridge ERC20: L2 → L1

interface IL2StandardBridge {
    function withdraw(
        address _l2Token,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;

    function withdrawTo(
        address _l2Token,
        address _to,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;
}

Withdrawal Lifecycle (L2 → L1)

Every L2→L1 withdrawal requires three L1 transactions:

  1. Initiate — Call withdraw on L2StandardBridge or L2CrossDomainMessenger. Produces a withdrawal hash.
  2. Prove — After the L2 output root containing your withdrawal is proposed on L1 (~1 hour), call proveWithdrawalTransaction on OptimismPortal.
  3. Finalize — After the 7-day challenge period, call finalizeWithdrawalTransaction on OptimismPortal.
import { getWithdrawals, getL2Output } from "viem/op-stack";

// After initiating withdrawal on L2, get the receipt
const l2Receipt = await publicClient.getTransactionReceipt({ hash: l2TxHash });

// Build withdrawal proof (after output root is proposed, ~1 hour)
const output = await getL2Output(l1Client, {
  l2BlockNumber: l2Receipt.blockNumber,
  targetChain: optimism,
});

// Prove on L1
const proveHash = await walletClient.proveWithdrawal({
  output,
  withdrawal: withdrawals[0],
  targetChain: optimism,
});

// Wait 7 days, then finalize on L1
const finalizeHash = await walletClient.finalizeWithdrawal({
  withdrawal: withdrawals[0],
  targetChain: optimism,
});

SuperchainERC20

SuperchainERC20 is a cross-chain token standard enabling native token transfers between OP Stack chains in the Superchain. Tokens implementing this standard can move between chains without traditional bridge locking.

Interface

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/// @notice Interface for tokens that support cross-chain transfers within the Superchain.
interface ICrosschainERC20 {
    /// @notice Emitted when tokens are minted via a cross-chain transfer.
    event CrosschainMint(address indexed to, uint256 amount, address indexed sender);

    /// @notice Emitted when tokens are burned for a cross-chain transfer.
    event CrosschainBurn(address indexed from, uint256 amount, address indexed sender);

    /// @notice Mint tokens on this chain as part of a cross-chain transfer.
    /// @dev Only callable by the SuperchainTokenBridge.
    function crosschainMint(address _to, uint256 _amount) external;

    /// @notice Burn tokens on this chain to initiate a cross-chain transfer.
    /// @dev Only callable by the SuperchainTokenBridge.
    function crosschainBurn(address _from, uint256 _amount) external;
}

Implementation

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import {ICrosschainERC20} from "./ICrosschainERC20.sol";

/// @dev SuperchainTokenBridge predeploy address — same on all OP Stack chains
address constant SUPERCHAIN_TOKEN_BRIDGE = 0x4200000000000000000000000000000000000028;

contract MySuperchainToken is ERC20, ICrosschainERC20 {
    constructor() ERC20("MySuperchainToken", "MST") {
        _mint(msg.sender, 1_000_000 * 1e18);
    }

    function crosschainMint(address _to, uint256 _amount) external override {
        require(msg.sender == SUPERCHAIN_TOKEN_BRIDGE, "Only bridge");
        _mint(_to, _amount);
        emit CrosschainMint(_to, _amount, msg.sender);
    }

    function crosschainBurn(address _from, uint256 _amount) external override {
        require(msg.sender == SUPERCHAIN_TOKEN_BRIDGE, "Only bridge");
        _burn(_from, _amount);
        emit CrosschainBurn(_from, _amount, msg.sender);
    }
}

Cross-Chain Transfer Flow

  1. User calls SuperchainTokenBridge.sendERC20 on the source chain
  2. Bridge calls crosschainBurn on the token contract (burns on source)
  3. A cross-chain message is relayed to the destination chain
  4. Bridge calls crosschainMint on the destination chain's token contract (mints on destination)

OP Stack

The OP Stack is the modular, open-source framework for building L2 blockchains. OP Mainnet, Base, Zora, Mode, and others are all OP Stack chains forming the Superchain.

Key Components

ComponentDescription
op-nodeConsensus client — derives L2 blocks from L1 data
op-gethExecution client — modified go-ethereum
op-batcherPosts transaction data to L1 (calldata or blobs)
op-proposerProposes L2 output roots to L1
op-challengerRuns fault proof games to challenge invalid proposals

Superchain

The Superchain is a network of OP Stack chains sharing:

  • Bridge contracts on L1
  • Sequencer coordination
  • Governance via the Optimism Collective
  • Interoperability messaging

Current Superchain members include OP Mainnet, Base, Zora, Mode, Fraxtal, Metal, and others. All share the same upgrade path and security model.

Building a Custom OP Chain

Use the OP Stack to launch your own chain:

# Clone the optimism monorepo
git clone https://github.com/ethereum-optimism/optimism.git
cd optimism

# Install dependencies
pnpm install

# Configure your chain (edit deploy-config)
# Deploy L1 contracts
# Start op-node, op-geth, op-batcher, op-proposer

Refer to the OP Stack Getting Started Guide for complete chain deployment.

Governance

The Optimism Collective governs the protocol through a bicameral system:

  • Token House — OP token holders vote on protocol upgrades, incentive programs, and treasury allocations
  • Citizens' House — Soulbound "citizen" badges vote on retroactive public goods funding (RetroPGF)

OP Token

PropertyValue
Address (L2)0x4200000000000000000000000000000000000042
Address (L1)0x4200000000000000000000000000000000000042 is the L2 predeploy; L1 address is 0x4200000000000000000000000000000000000042 bridged
Total supply4,294,967,296 (2^32)
TypeGovernance only (no fee burn or staking yield)

Delegation

OP token holders delegate voting power to active governance participants:

import { parseAbi } from "viem";

const opTokenAbi = parseAbi([
  "function delegate(address delegatee) external",
  "function delegates(address account) external view returns (address)",
  "function getVotes(address account) external view returns (uint256)",
]);

const OP_TOKEN = "0x4200000000000000000000000000000000000042" as const;

// Delegate voting power
const hash = await walletClient.writeContract({
  address: OP_TOKEN,
  abi: opTokenAbi,
  functionName: "delegate",
  args: [delegateAddress],
});

Key Differences from Ethereum

FeatureEthereumOP Mainnet
Block time12 seconds2 seconds
Gas pricingSingle base feeL2 execution + L1 data fee
block.numberL1 block numberL2 block number
Finality~15 minutes (2 epochs)7 days for L2→L1 (challenge period)
SequencingDecentralized validatorsCentralized sequencer (OP Labs)
PREVRANDAOBeacon chain randomnessSequencer-set value (NOT random, do NOT use for randomness)
PUSH0Supported (Shanghai+)Supported
block.difficultyAlways 0 post-mergeAlways 0

Opcodes Differences

  • PREVRANDAO (formerly DIFFICULTY) — Returns the sequencer-set value, NOT true randomness. Never use for on-chain randomness. Use Chainlink VRF or a commit-reveal scheme.
  • ORIGIN / CALLER — Work normally for L2 transactions. For L1→L2 deposits, the origin is aliased (see Sender Aliasing).
  • All other opcodes behave identically to Ethereum.

Unsupported Features

  • No native account abstraction (EIP-4337) — Use third-party bundlers (Pimlico, Alchemy, Stackup).
  • No eth_getProof with pending block tag — Use latest instead.

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