Anvil Local Node

Anvil is Foundry's fast local Ethereum node for development and testing.

When to Use

•Local development and testing
•Forking mainnet or other networks
•Integration testing with frontend applications
•Testing transaction flows before mainnet
•Simulating complex scenarios

Quick Start

bash

# Start local node with 10 pre-funded accounts
anvil

# Start with custom port
anvil --port 8545

# Start with specific accounts
anvil --accounts 5 --balance 1000

Default Configuration

When started without flags:

Setting	Value
Port	8545
Accounts	10
Balance	10000 ETH each
Chain ID	31337
Block time	Instant (mines on each tx)

Pre-Funded Accounts

Default test accounts (deterministic):

code

Account #0: 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
Private Key: 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80

Account #1: 0x70997970C51812dc3A010C7d01b50e0d17dc79C8
Private Key: 0x59c6995e998f97a5a0044966f0945389dc9e86dae88c7a8412f4603b6b78690d

Account #2: 0x3C44CdDdB6a900fa2b585dd299e03d12FA4293BC
Private Key: 0x5de4111afa1a4b94908f83103eb1f1706367c2e68ca870fc3fb9a804cdab365a

Forking

Fork Mainnet

bash

# Fork at latest block
anvil --fork-url https://eth-mainnet.g.alchemy.com/v2/$API_KEY

# Fork at specific block (reproducible)
anvil --fork-url $MAINNET_RPC --fork-block-number 18000000

Fork Other Networks

bash

# Arbitrum
anvil --fork-url https://arb1.arbitrum.io/rpc

# Optimism
anvil --fork-url https://mainnet.optimism.io

# Base
anvil --fork-url https://mainnet.base.org

# Polygon
anvil --fork-url https://polygon-rpc.com

Configuration Options

Account Settings

bash

# Custom number of accounts
anvil --accounts 20

# Custom balance (in ETH)
anvil --balance 100000

# Use specific mnemonic
anvil --mnemonic "test test test test test test test test test test test junk"

# Derivation path
anvil --derivation-path "m/44'/60'/0'/0/"

Network Settings

bash

# Custom chain ID
anvil --chain-id 1337

# Custom port
anvil --port 8546

# Listen on all interfaces
anvil --host 0.0.0.0

# Custom gas limit
anvil --gas-limit 30000000

# Custom gas price
anvil --gas-price 1000000000

Mining Settings

bash

# Auto-mine (default - instant blocks)
anvil

# Interval mining (block every N seconds)
anvil --block-time 12

# No mining (manual only)
anvil --no-mining

State Management

bash

# Load state from file
anvil --load-state state.json

# Dump state to file on exit
anvil --dump-state state.json

# State snapshot directory
anvil --state ./anvil-state

Forking Features

See forking.md for detailed patterns.

Impersonating Accounts

bash

# Start with unlocked accounts
anvil --fork-url $RPC --unlocked 0xWhaleAddress

Or via RPC:

bash

# Unlock account
cast rpc anvil_impersonateAccount 0xWhaleAddress

# Send as whale
cast send 0xRecipient --value 100ether \
    --from 0xWhaleAddress \
    --unlocked

# Stop impersonating
cast rpc anvil_stopImpersonatingAccount 0xWhaleAddress

Time Manipulation

bash

# Increase time
cast rpc evm_increaseTime 86400  # 1 day

# Set timestamp
cast rpc evm_setNextBlockTimestamp 1700000000

# Mine block with new timestamp
cast rpc evm_mine

Block Manipulation

bash

# Mine N blocks
cast rpc anvil_mine 10

# Set block gas limit
cast rpc evm_setBlockGasLimit 50000000

RPC Methods

Standard Ethereum RPC

All standard Ethereum JSON-RPC methods are supported.

Anvil-Specific Methods

bash

# Mine blocks
cast rpc anvil_mine [numBlocks]

# Set balance
cast rpc anvil_setBalance 0xAddress 0x8ac7230489e80000  # 10 ETH in hex

# Set code
cast rpc anvil_setCode 0xAddress 0x608060...

# Set storage
cast rpc anvil_setStorageAt 0xContract 0x0 0x1

# Impersonate
cast rpc anvil_impersonateAccount 0xAddress

# Snapshot
SNAPSHOT_ID=$(cast rpc evm_snapshot)

# Revert to snapshot
cast rpc evm_revert $SNAPSHOT_ID

# Set nonce
cast rpc anvil_setNonce 0xAddress 100

# Set chain ID
cast rpc anvil_setChainId 1

Integration with Forge

Fork Testing

solidity

contract ForkTest is Test {
    function setUp() public {
        // Fork mainnet at specific block
        vm.createSelectFork("mainnet", 18000000);
    }

    function test_ForkState() public {
        // Tests run against forked state
        IERC20 usdc = IERC20(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);
        assertGt(usdc.totalSupply(), 0);
    }
}

Running Against Anvil

bash

# Terminal 1: Start Anvil
anvil --fork-url $MAINNET_RPC

# Terminal 2: Run tests
forge test --rpc-url http://localhost:8545

Common Use Cases

Frontend Development

bash

# Start persistent forked node
anvil --fork-url $MAINNET_RPC --dump-state ./state.json

# Connect frontend to http://localhost:8545
# Chain ID: 31337

Integration Testing

bash

# Start Anvil in background
anvil --fork-url $MAINNET_RPC &

# Deploy contracts
forge script script/Deploy.s.sol --rpc-url http://localhost:8545 --broadcast

# Run integration tests
forge test --rpc-url http://localhost:8545

# Stop Anvil
pkill anvil

Debugging Transactions

bash

# Fork at block before problematic tx
anvil --fork-url $RPC --fork-block-number 17999999

# Replay transaction
cast send --rpc-url http://localhost:8545 ...

# Debug with traces
cast run $TX_HASH --rpc-url http://localhost:8545

Best Practices

•Use specific fork blocks for reproducible tests
•Save state for faster restarts during development
•Use unlocked accounts for impersonation testing
•Set appropriate block time for time-sensitive tests
•Monitor memory usage when forking large state

Troubleshooting

Connection Issues

bash

# Check if Anvil is running
curl http://localhost:8545 -X POST -H "Content-Type: application/json" \
    --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

Memory Issues

bash

# Limit cache size
anvil --fork-url $RPC --fork-retry-backoff 1000

# Use specific block to limit state
anvil --fork-url $RPC --fork-block-number 18000000

RPC Rate Limits

bash

# Add retry backoff
anvil --fork-url $RPC --fork-retry-backoff 1000

# Use multiple RPC endpoints (via load balancer)