Verify smart contracts with Foundry Forge

Verify Solidity smart contracts on Blockscout directly from the Foundry toolchain using Forge’s built-in verification support and CLI flags.

Foundry is a smart contract development toolchain. Foundry manages your dependencies, compiles your project, runs tests, deploys, and lets you interact with the chain from the command line and via Solidity scripts.

Forge is a command-line tool that ships with Foundry. Forge tests, builds, and deploys your smart contracts. Forge supports contract verification out of the box (https://www.getfoundry.sh/reference/forge/verify-contract).

Verify contract

In forge, contracts can be verified at the time of deployment (e.g. using forge script or forge create), or later if the contracts are already deployed (e.g. using forge verify-contract).

This guide uses the Blockscout PRO API, which covers every Blockscout-supported chain with a single key. Swap the chain_id value to move between chains, no per-chain setup required. Get a free key at dev.blockscout.com.

Tips:

1. Specify the --verifier=blockscout flag to use the Blockscout verification provider.
2. Specify --verifier-url="https://api.blockscout.com/v2/api?chain_id=<chain_id>", swapping <chain_id> for the chain you deployed to (e.g. chain_id=1 for Ethereum mainnet, chain_id=8453 for Base). See the full list of supported chains at dev.blockscout.com.
3. Pass your PRO API key with --etherscan-api-key <your_pro_api_key>. Forge uses this flag name for all Etherscan-compatible verifiers, including Blockscout.
4. You can specify most configuration options (e.g., evm version, disabling optimizations) via the usual Forge configuration.

Example (Deploy and verify)

Verify a contract with Blockscout right after deployment:

forge create \
  --rpc-url <rpc_https_endpoint> \
  --private-key $PRIVATE_KEY \
  <contract_file>:<contract_name> \
  --verify \
  --verifier blockscout \
  --verifier-url "https://api.blockscout.com/v2/api?chain_id=<chain_id>" \
  --etherscan-api-key <your_pro_api_key>

Or if using Foundry scripts:

forge script <script_file> \
  --rpc-url <rpc_https_endpoint> \
  --private-key $PRIVATE_KEY \
  --broadcast \
  --verify \
  --verifier blockscout \
  --verifier-url "https://api.blockscout.com/v2/api?chain_id=<chain_id>" \
  --etherscan-api-key <your_pro_api_key>

Example (Verify already deployed contract)

forge verify-contract \
  --rpc-url <rpc_https_endpoint> \
  <address> \
  <contract_file>:<contract_name> \
  --verifier blockscout \
  --verifier-url "https://api.blockscout.com/v2/api?chain_id=<chain_id>" \
  --etherscan-api-key <your_pro_api_key>

Or if using Foundry scripts for the last executed script run:

forge script <script_file> \
  --rpc-url <rpc_https_endpoint> \
  --private-key $PRIVATE_KEY \
  --resume \
  --verify \
  --verifier blockscout \
  --verifier-url "https://api.blockscout.com/v2/api?chain_id=<chain_id>" \
  --etherscan-api-key <your_pro_api_key>

Verifying against a specific instance

If you’re running a self-hosted Blockscout instance, or verifying on a chain the PRO API doesn’t cover yet, point Forge at that instance’s own API instead. No API key is required for this route.

forge verify-contract \
  --rpc-url <rpc_https_endpoint> \
  <address> \
  <contract_file>:<contract_name> \
  --verifier blockscout \
  --verifier-url <blockscout_homepage_explorer_url>/api/

Make sure to add /api/ to the end of the Blockscout homepage explorer URL (e.g., --verifier-url=https://eth-sepolia.blockscout.com/api/). The same --verify flag works with forge create and forge script, following the patterns above.

Do I need a real API key?

For the PRO API, yes. Get a free key at dev.blockscout.com. For the per-instance route, no: any non-empty string works, or you can drop --etherscan-api-key entirely.

Which chains does the PRO API cover?

Every Blockscout-indexed mainnet and testnet, under one key. Check the current list at dev.blockscout.com.

Resources

Learn more about Forge’s verification flags at https://www.getfoundry.sh/reference/forge/verify-contract