Smart contract verification on Polygonscan
Deployed contract without verified source code is a black box. Polygonscan shows only bytecode. Users can't read logic, integrators can't generate ABI, auditors work with decompiled code instead of original. Verification is not bureaucracy, it's minimum transparency standard for any production contract.
Why verification breaks
Most common reason for failure — compiler parameter mismatch. Polygonscan compiles uploaded source code and compares bytecode with deployed. If compiler version, optimization flag, or runs count differs even by one — verification fails without clear error message.
Second reason: flattened code with duplicate license identifiers or pragma statements. Tools like hardhat flatten sometimes leave multiple // SPDX-License-Identifier and multiple pragma solidity — Polygonscan rejects this.
For contracts with constructor arguments verification requires ABI-encoded arguments in hex. Incorrectly encoded arguments — another typical failure reason.
How we verify
Use Hardhat Etherscan plugin (@nomicfoundation/hardhat-verify) or forge verify-contract from Foundry — both support Polygonscan via same API key. Verification runs automatically in deploy script immediately after deployment, while compiler parameters exactly known from build artifacts.
For proxy contracts additionally verify implementation and link to proxy via Polygonscan UI ("Is this a proxy?"). After linking users see implementation functions through proxy address.
Standard process: deploy → auto-verification via CLI → manual check on Polygonscan → proxy linking if needed. Takes 2-3 hours including indexing wait.