explorer-contract-verification
Testing & QualityVerify 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.
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How to use this skill
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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.