How to detect if an ethereum address is an ERC20 token contract

Question

If only get an ethereum address from input, is there anyway to find out whether it match ERC20?

Answer 1

There are many possible ways to achieve this. One possible quick and dirty solution is to check if a ERC20 function exists on the contract address by calling the following:

eth.call({to:contractAddress, data:web3.sha3("balanceOf(address)")})

A non-ERC20 will return a 'null' 0x hex response whereas an ERC20 will give you a 32byte uint, in this case 0 but if you provide an address in the data then it will give you the actual token balance for that address.

This is not a guaranteed way of determining a contract is ERC20 since other contracts may expose the same function, however it is a quick and easy check. You could add additional calls on totalSupply() etc. for more confirmation.

Hope this helps!

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