24 votes
Accepted

How to find solidity code for a contract address

Mainly due to optimizations carried out when the source code is compiled it's not feasible to get the source code from the bytecode/opcode itself. Refer this question. Compilation back to the ...
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18 votes
Accepted

Normal transactions VS. Internal transactions in etherscan

Internal transactions, despite the name (which isn't part of the yellowpaper; it's a convention people have settled on) aren't actual transactions, and aren't included directly in the blockchain; they'...
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  • 9,403
17 votes
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How to verify token after etherscan, and submit icon

I don't know if the process to verify has changed, but you need to send your ICON image by e-mail. To do this you’ll need to go to the Etherscan Contact Us Page and send them an e-mail with the ...
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15 votes

Normal transactions VS. Internal transactions in etherscan

In the Ethereum protocol there's only transactions and message calls. A transaction is a type of message call. A transaction may perform other message calls, but these are not transactions (even ...
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  • 78.8k
15 votes

How do I find the exact solidity compiler version used by truffle?

I'm running Truffle 3.4.11 and running just: truffle version gives me the Solidity version as well: truffle version ...
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  • 331
14 votes
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How do fronrunning and sniper bots work?

A good overview of frontrunning, and related miner extractable value (MEV), problems are well established and well known at this point. The difference between these two modes of frontrunning that in ...
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12 votes

Normal transactions VS. Internal transactions in etherscan

An internal transaction is not a real transaction - it has no signature and is not included in the blockchain. It is the result of a contract initiating a value transfer, or calling another contract, ...
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  • 724
12 votes
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Etherscan: How can I verify a contract with multiple imports deployed with Truffle?

Currently etherscan does not support verification of multifile contracts. But there is discussion on etherscan's reddit about this issue. Concatenating files into one worked some time ago, but since ...
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  • 2,896
12 votes
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How do I get the implementation contract address from the proxy contract address?

Most proxy contracts typically have a public variable defined as a: address public implementation; Which defines the address of the implementation contract. You could then call it as a view function ...
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11 votes
Accepted

Obtain token transfer data from an address

How about using Etherscan's Event Log API? https://api.etherscan.io/api?module=logs&action=getLogs &fromBlock=0 &toBlock=latest &address=[Token Contract Address] &...
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  • 8,702
11 votes

Etherscan API Invalid API key

I had this problem. The API Key seems to take about five minutes to activate once it is created.
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10 votes

How do you verify a contract on etherscan that is deployed by another contract?

It is not possible as on 24th March 2018. Etherscan is unable to locate contract code on the address of subcontract. Here is the transaction which deploys two contracts. But for the second contract, ...
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  • 1,650
9 votes
Accepted

How to get an ERC20 token listed in etherscan.io

Etherscan's FAQ page answers your first question in the "Token Tracker Listings" section. Here is what it says: Any compatible ERC20 tokens on the Ethereum blockchain can be publicly and ...
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  • 2,249
9 votes

Etherscan API - Get all token balances

As previously mentioned it doesn't appear possible using etherscan. But it's possible using the (free) ethexplorer.io API. The format is: http://api.ethplorer.io/getAddressInfo/[YOUR_ADDRESS]?apiKey=...
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9 votes
Accepted

What's the meaning of "similar match" in source verification?

Here is the reply I got from Kaven @Etherscan, in case it's useful for somebody else: Contract that gets the “Similar Match” annotation has the identical contract code (exact bytecode) with ...
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  • 141
9 votes
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How to manually approve a token for swap on Uniswap (direct contract interaction)

Get the pool address Go to the Uniswap UI at https://app.uniswap.org/. Choose the token pair you want and then click the View pair analytics ↗. This will take you to a link like https://uniswap.info/...
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8 votes
Accepted

Are pending transactions "dropped" and "reinstated"?

My understanding is that your understanding is correct, except you're missing one particular property of the Ethereum node software. Namely, as part of #3, the transaction is stored in the node's ...
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  • 6,550
8 votes
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What's difference between "Gas Used By Txn" and "Cumulative Gas Used" fields?

Gas Used By Txn - gas used by the transaction Cumulative Gas Used - gas used by the transaction plus gas used by the transactions executed before the current one in the same block. Cumulative gas is ...
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  • 10.3k
8 votes
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Etherscan verification purpose

It verifies that the bytecode of the smart contract which is stored in the Ethereum network corresponds to the Solidity code initially available only to the smart contract developer. Etherescan ...
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  • 10.3k
8 votes
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How does etherscan fetch the number of token holders from a smart contract?

They keep track of Transfer events emitted by that smart contract. Most likely they record them in an SQL database and maintain a ledger based on these events. The event is defined in the ERC20 https:/...
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  • 10.3k
8 votes

How do I get the latest block using etherscan api?

Even easier: https://api.blockcypher.com/v1/eth/main Blockcypher is a pretty good api for this kind of stuff.
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8 votes
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weird transaction sending to self

It's about canceling a transaction. More precisely, it's a replacement transaction for something else that was in the pending transaction pool. Consider a case where a transaction is sent with ...
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  • 51.8k
8 votes

My friend sent me a screenshot of a transaction hash, but when I search for it I find divergent data. What happened?

Your friend simply edited the HTML and changed the TimeStamp, To, and Value on that page. You can tell this because all of the other stats on the page are correct, with the exception of the items ...
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8 votes
Accepted

I got "sandwich attacked" on my transaction

You are not providing enough information about your case, but most likely you have been front-run. When you are giving away free money on the blockchain, some people will take it. When you announce ...
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  • 3,426
7 votes
Accepted

How does Etherscan work?

If you want to do analytics, the trick is scrapping the whole blockchain into an indexed database. My advice is that you get a SQL database, and write a program that queries a node for its blocks, one ...
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  • 2,351
7 votes

How does EtherScan know I am sending to a Shapeshift/Poloniex wallet?

How does EtherScan know I am sending to a Shapeshift/Poloniex wallet? The short answer is that the From: and To: wallet (also known as account or address) details are sent along with the transaction ...
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7 votes
Accepted

How to get details for an Ethereum transaction

EtherScan API also provides a API for transaction details which I missed. It's part of Geth/Parity Proxy APIs by name eth_getTransactionByHash
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  • 625
7 votes

Flatten Truffle Solidity Contracts for Etherscan's `Verify Contract Code` Feature

I've used this one in the past, with very good results and minimal setup: https://github.com/oraclesorg/oracles-combine-solidity git clone https://github.com/oraclesorg/oracles-combine-solidity cd ...
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  • 7,286
7 votes
Accepted

What does a position means in an ethereum Tx?

Nonce is the number of transactions the source account has made so far starting from 0, not from 1, position is the number of this transaction (mined) inside the block.
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  • 3,426
7 votes
Accepted

How is it possible for 0x0000000000000000000000000000000000000000 to send out ERC-20 tokens?

Per the ERC20 standard, newly created ERC20 tokens are sent from 0x0000000000000000000000000000000000000000 to the address they are meant to be sent to. It was done as a way of logging and to avoid ...
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