Etherscan Guide: How to Verify Smart Contracts

On Etherscan, verifying a smart contract means publishing its readable source code and letting Etherscan prove that code matches the program actually running at that address on Ethereum. A verified contract carries a green tick on its Contract tab and anyone can read what it does. An unverified one is a sealed box. Checking a contract takes seconds; verifying your own takes about ten minutes.

What does the green tick really prove?

Only that the published text compiles into exactly the code sitting at that address - like a recipe that provably produces the cake in front of you. It says nothing about whether the recipe is any good. Uniswap and Aave are verified and have been read by thousands of developers for years. A scam token can be verified too, and still be written to trap you. Verified means visible, not trustworthy.

How do you check whether a contract is verified?

Search the address or token on Etherscan and open the Contract tab. A green tick and the words "Contract Source Code Verified" mean the code is there to read, along with Read Contract and Write Contract tabs that let you query it directly. No tick means nobody outside the team can see what the code does. Check the creation date on the same page while you are there: a project claiming years of history from a contract deployed on Tuesday has told you everything you need to know.

How do you verify a contract you deployed?

Open the address, choose Verify and Publish, and supply four things: the exact compiler version, whether the optimizer was on and for how many runs, the full source including every imported file, and the constructor arguments. Easier still, let your tools do it - Hardhat and Foundry both ship a verify command that sends all of this through the Etherscan API in one line. If verification fails with a bytecode mismatch, the cause is almost always the compiler version or an optimizer setting that differs from the one used at deployment.

Make the Contract tab a reflex before you approve anything in MetaMask, especially a token a stranger told you about. Then read how to use Etherscan to check transactions and how to check and revoke token approvals.