Smart Contract Verification on BscScan
A deployed contract without verified source code is bytecode on the blockchain. BscScan shows transactions but doesn't show what the function actually does. Users can't read the logic, auditors work only with decompiled code, and Read/Write Contract integrations are unavailable. Verification turns bytecode back into readable Solidity.
Why Verification Sometimes Fails
The most common cause of failure is bytecode mismatch. BscScan recompiles the uploaded source with the specified parameters and compares it to the on-chain bytecode. If the compiler version differs, optimizer runs differ, or evmVersion doesn't match — the result won't match.
Flattening contracts with dependencies. If a contract imports OpenZeppelin, you either upload all files via Standard JSON Input or flatten into one file. Flattening via hardhat flatten sometimes duplicates SPDX-License-Identifier and pragma solidity — this is a compilation error. Keep one directive at the beginning of the file.
Immutable variables. immutable variables are written into bytecode during deployment with specific values. Verification via standard form sometimes doesn't allow correctly specifying constructor arguments for immutable — Standard JSON Input is more reliable.
How We Verify
Three methods, from simple to reliable:
Via Hardhat Verify plugin. Single command after deployment:
npx hardhat verify --network bsc DEPLOYED_ADDRESS "arg1" "arg2"
The plugin automatically detects compiler version, optimizer settings from hardhat.config.ts, and forms a correct request to BscScan API. Works for most cases.
Standard JSON Input. For complex projects with many dependencies. Foundry generates it via forge verify-contract or you can get it via hardhat compile --show-stack-traces. JSON contains all sources, compiler settings, metadata. Upload via BscScan UI in "Standard Json-Input" tab.
API verification. For CI/CD: POST request to https://api.bscscan.com/api with API key. Used in automatic deployment — script deploys and immediately verifies. Foundry supports this natively via --verify --etherscan-api-key.
Timeline
Verification of one contract — 1-2 hours. If the contract is already deployed and there are no sources with exact compiler parameters — up to several hours to recover configuration through bytecode analysis.