explorer-contract-verification

name	explorer-contract-verification
description	Verify smart contracts on Etherscan, Routescan, and Blockscout block explorers. This skill should be used when the user asks to "verify contract", "verify on etherscan", "verify on blockscout", "verify on routescan", "verify on chain scan". Handles standard verification, Etherscan V2 API, Routescan, Blockscout verification, proxy patterns, and factory-created contracts.

Overview

Contract verification on Etherscan, Routescan, and Blockscout explorers using Foundry's forge verify-contract. Covers standard Etherscan verification, unsupported chains via Etherscan V2 API, Routescan, Blockscout verification, proxy patterns, and factory-created contracts.

When to Use

• Verify deployed smart contracts on Etherscan, Routescan, or Blockscout explorers
• Verify proxy contracts (ERC1967, UUPS)
• Verify factory-created contracts (CREATE2)
• Extract constructor arguments from deployment data

Prerequisites

Requirement	How to Get
Foundry ≥1.3.6	Run forge -V to check version
Contract address	From deployment broadcast or user
Chain ID	From explorer or network configuration
Explorer API key	From Etherscan account (Etherscan chains only)
Source code	Must match deployed bytecode exactly

Version Check

Before proceeding, verify Foundry version:

forge -V

Stop if version is below 1.3.6.

Chain Reference

Determine the correct verification method by looking up the target chain below.

Etherscan Chains

Chain	Chain ID	Method
abstract	2741	Etherscan V2
arbitrum	42161	Native or V2
base	8453	Native or V2
berachain	80094	Etherscan V2
bsc	56	Native or V2
ethereum	1	Native or V2
gnosis	100	Native or V2
linea	59144	Etherscan V2
optimism	10	Native or V2
polygon	137	Native or V2
scroll	534352	Etherscan V2
sonic	146	Etherscan V2
unichain	130	Etherscan V2
arbitrum_sepolia	421614	Native or V2
base_sepolia	84532	Native or V2
optimism_sepolia	11155420	Native or V2
sepolia	11155111	Native or V2

Routescan Chains

Chain	Chain ID	Verifier URL
avalanche	43114	https://api.routescan.io/v2/network/mainnet/evm/43114/etherscan/api
chiliz	88888	https://api.routescan.io/v2/network/mainnet/evm/88888/etherscan/api

Blockscout Chains

Chain	Chain ID	Verifier URL
lightlink	1890	https://phoenix.lightlink.io/api/
mode	34443	https://explorer.mode.network/api/
morph	2818	https://explorer-api.morphl2.io/api/
superseed	5330	https://explorer.superseed.xyz/api/

Verification Methods

Method 1: Etherscan — Native Support

For chains Foundry supports natively:

FOUNDRY_PROFILE=optimized forge verify-contract \
  <CONTRACT_ADDRESS> \
  src/<Contract>.sol:<Contract> \
  --rpc-url <chain_name> \
  --verifier etherscan \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --watch

Method 2: Etherscan V2 API

When Foundry shows "No known Etherscan API URL for chain X", or for any Etherscan chain:

FOUNDRY_PROFILE=optimized forge verify-contract \
  <CONTRACT_ADDRESS> \
  src/<Contract>.sol:<Contract> \
  --verifier etherscan \
  --verifier-url "https://api.etherscan.io/v2/api?chainid=<CHAIN_ID>" \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --watch

Supported chains: https://docs.etherscan.io/supported-chains

Method 3: Routescan

For chains using Routescan explorers (avalanche, chiliz). Look up the verifier URL from the Routescan Chains table above. Uses --verifier etherscan with a Routescan URL.

FOUNDRY_PROFILE=optimized forge verify-contract \
  <CONTRACT_ADDRESS> \
  src/<Contract>.sol:<Contract> \
  --verifier etherscan \
  --verifier-url "<ROUTESCAN_VERIFIER_URL>" \
  --etherscan-api-key "verifyContract" \
  --watch

Note: Routescan does not require a real API key — pass "verifyContract" as the value.

Method 4: Blockscout

For chains using Blockscout explorers. Look up the verifier URL from the Blockscout Chains table above.

FOUNDRY_PROFILE=optimized forge verify-contract \
  <CONTRACT_ADDRESS> \
  src/<Contract>.sol:<Contract> \
  --verifier blockscout \
  --verifier-url "<BLOCKSCOUT_VERIFIER_URL>" \
  --etherscan-api-key "verifyContract" \
  --watch

Note: Blockscout does not require a real API key — pass "verifyContract" as the value.

Constructor Arguments

Append --constructor-args to any method above when the contract has constructor parameters:

--constructor-args <ABI_ENCODED_ARGS>

Generate constructor args with cast abi-encode:

cast abi-encode "constructor(address,uint256)" 0x123... 1000

Special Cases

Reference: ./references/special-cases.md

Proxy Contracts

Verify implementation and proxy separately. See reference for ERC1967 pattern.

Factory-Created Contracts

Extract constructor args from broadcast initCode using scripts/extract_constructor_args.py.

Library Verification

For libraries, use full path:

src/libraries/<Library>.sol:<Library>

Troubleshooting

Reference: ./references/troubleshooting.md

Common Issues

Error	Cause	Solution
"No known Etherscan API URL"	Chain not in Foundry	Use --verifier-url with V2 API
"Bytecode does not match"	Compilation drift	Checkout deployment commit + reinstall deps
"Constructor args mismatch"	Wrong/missing args	Extract from broadcast or encode manually
"Already verified"	Previously verified	No action needed

Output

After successful verification:

• Contract source visible on explorer
• ABI available for interaction
• Constructor args decoded
• "Contract Source Code Verified" badge

Examples

Reference: ./references/examples.md for real-world verification examples from Monad deployment.