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48 votes
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ERC20 vs ERC223. List of differences

3 Primary improvements with ERC223 Eliminates the problem of lost tokens which happens during the transfer of ERC20 tokens to a contract (when people mistakenly use the instructions for sending ...
Tesa's user avatar
  • 2,269
37 votes
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How do I convert my The DAO tokens into ethers using the withdrawal contract after the hard fork?

Update Mar 29 2017 The latest instructions can be found at The DAO Refunds. Notes This Withdrawal contract only allows the conversion of The DAO tokens (DAO) into ethers (ETH) at the rate of 100 ...
BokkyPooBah's user avatar
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35 votes
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Getting ABI data for ERC20 tokens programatically with Web3

Thank you K.Fichter for the help, I just want to fully clarify the answer for anyone else who may run into this issue. Let's say you want to get the balance of a token at an Ethereum Address. Using ...
Shawn Tabrizi's user avatar
26 votes

Decimals on ERC20 Tokens

The way I think about this is that the number of tokens is: tokenSupply = tokensIActuallyWant * (10 ** decimals) If I want 1 token with the ability to subdivide it with a precision of 2 decimal places,...
xflowXen's user avatar
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26 votes
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If someone found a private key to 0x0, would they be able to access all the tokens (over one billion dollars worth) stored there?

Hypothetically speaking, yes. If someone managed to guess a private key to 0x0, then they would have full control over all ether/tokens belonging to that address. It is so unlikely that it's ...
natewelch_'s user avatar
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23 votes
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Paying a transaction fee with an ERC20 token

It is not really true at the moment that you can pay fees in anything except ETH, although there is some discussion about changing this. The way things normally work, you have to pay the fee in ETH. ...
Edmund Edgar's user avatar
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22 votes
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Is there length limits on Token Symbols?

I used the CoinMarketCap API to pull down a list of all registered currencies and assets (so not just ERC-20 tokens... ), and fed it into a quick Python script to count the number of occurrences of ...
Richard Horrocks's user avatar
22 votes

Send tokens using approve and transferFrom vs only transfer

Transfer method The transfer method is for a 2 party transfer, where a sender wishes to transfer some tokens to a receiver. Sender ➜ transfer(receiver, amount) Approve and transferFrom method The ...
supakaity's user avatar
  • 1,468
19 votes

What is a sidechain?

Sidechain is a blockchain that runs in parallel to the main blockchain which extends functionality through interoperable blockchain networks allowing a decentralized way of transferring/synchronizing ...
kenorb's user avatar
  • 1,171
19 votes

Best way to burn ethers and other ethereum tokens?

According to Jeff Wilcke, the right way to burn ETH is to create a contract which immediately self destructs and sends to its own address, or just send ether to his deployed contract which does it all ...
maurelian's user avatar
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19 votes
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How to infer token price from ethereum blockchain UniSwap data?

“The price of a given token on a given exchange can be calculated as the exchange contract's token_balance divided by its ether_balance.” This description means: On-chain price: In opposed to off-...
goodvibration's user avatar
17 votes

what does `wad`stand for

A wad is a decimal number with 18 digits of precision that is being represented as an integer. A ray is a decimal number with 27 digits of precision that is being represented as an integer. Under the ...
Raman Shalupau's user avatar
17 votes
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Where can I find ERC20 token faucets for testing?

From Weenus 💪 ERC20 FaucetAnnouncing the Weenus 💪 ERC20 token faucets on the Ethereum mainnet, and Ropsten, Kovan, Rinkeby and Görli testnets: Search in your Ethereum blockchain explorer for WEENUS ...
BokkyPooBah's user avatar
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16 votes
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Binance Smart Chain tokens: What are tTotal, rTotal, tSupply, rSupply, rOwned, tOwned which I see everywhere?

It' a bit of an algorithm, or really just some math, to to the balance of an account. Instead of using the default "tokenSupply". Constants Fee is 1% (assuming no burn, just a general 1% ...
Bob Linux's user avatar
  • 348
15 votes
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Why most ERC-20 Tokens Have 18 Decimals?

Ether itself has 18 decimals, most ERC-20 tokens simply follow that standard. 1 ETH is represented by 10^18 of its natural unit ( 1 Ether = 1,000,000,000,000,000,000 wei ). This offers you much ...
Xilis's user avatar
  • 312
14 votes
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What are the key criteria for meeting the ERC20 token standard?

At a high level, the main parts of ERC20 specify: 1. how tokens can be transferred by its owner 2. how tokens can be transferred on behalf of an owner 3. how to get data about the token 4. events ...
eth's user avatar
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13 votes
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How do I convert my The DAO tokens into ethers on the Ethereum Classic chain?

Update Apr 12 2017 There are only 3 more days to withdraw your refunds from the WhitehatWithdraw contract. There are still 1,651,062.7506 ETC (USD 4,292,763.15) remaining in the withdrawal contract. ...
BokkyPooBah's user avatar
  • 40.3k
13 votes
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How can ERC20 token implementations be verified?

I think it has to ultimately be human verification, unless it exactly matches an existing contract that's already been verified by humans. Even if all the functions that are supposed to be in the ...
Edmund Edgar's user avatar
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13 votes
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Why does my smart contract tokens not show up in MyEtherWallet or MetaMask?

You need to give Metamask the address of the token itself, not the address of the contract that created the token, like you did. I made the same mistake myself.
memius's user avatar
  • 246
12 votes
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How do I get a refund for the amount I paid in excess of 1 ether to 100 The DAO tokens

Update Mar 29 2017 The latest instructions can be found at The DAO Refunds. At the hard-fork block #1,920,000 , the ETH balance from The DAO and it's child DAOs (which includes the balance from the ...
BokkyPooBah's user avatar
  • 40.3k
12 votes
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web3.js can I call a smart contract function without knowing the ABI?

I'm posting a proper answer here - thanks to @smarx, and others off SO who helped lead me to this solution. The answer This can be done if you know the method signature (including the types of the ...
Kris Randall's user avatar
12 votes
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ERC-165 query on ERC-721 implementation

supportsInterface shouldn't be used to check individual functions. Each interface should have a single interfaceID which, as you can see in the ERC-721 implementation you posted, is constructed as ...
AnAllergyToAnalogy's user avatar
12 votes

Someone sent 0 ETH to my contract and got 134100 tokens

It wasn't just just "someone"... it was the contract creator who made the transaction, and there is a function called mintTokens which allows them to exactly do this. /** * Allows owner to create ...
Shawn Tabrizi's user avatar
11 votes

What is the purpose of interface contracts?

Interface contracts work like other interface agreements in traditional object oriented languages. In your example, the interface specifies the functions a contract of type TokenInterface must ...
dbryson's user avatar
  • 6,393
11 votes

How to get tokens out of a metamask account

Thanks for asking, this is a common question but did not have a good public answer. I've updated the MetaMask user FAQ to include a response, and am copying that answer here: MetaMask does not ...
DanF's user avatar
  • 2,626
11 votes
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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] &...
benjaminion's user avatar
  • 9,297
11 votes
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Are ERC20 token names unique?

There could be any number of ERC20 contracts deployed with the name string variable "Golem Network Token." However, each one of these contracts has a unique Ethereum contract address. The ERC20 ...
CBobRobison's user avatar
  • 1,245
11 votes
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how to get list of transactions history about specific contract address using web3?

Getting all transaction history requires you to iterate over each and every block since the contract creation. As you might guess, this would be extremely slow, plus it depends on your Infura plan: ...
kmotoko's user avatar
  • 266
10 votes
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How can I find out the token balance of some address?

There are 2 ways using https://etherscan.io/ : Navigate to https://etherscan.io/ . Enter the account in the search box on the top right, the click Go. If there are tokens associated with the account, ...
BokkyPooBah's user avatar
  • 40.3k
10 votes

Accepting an ERC20 Token as Payment

If you want to receive ERC20 tokens onto a new contract along with data, you can create the new contract using ERC 223 token standard. Read here (Dont be confused about the nomenclature, its ERC223 ...
aviral agrawal's user avatar

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