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ERC-20 is the technical standard upon which the issuance of smart contracts on the Ethereum blockchain is based. "ERC-20" refers to Ethereum Request for Comment #20, which was a format for standards development used earlier by the Ethereum Foundation.


Tokens are digital assets which represent contracts that can have value. All tokens on the Ethereum blockchain use ERC-20, which allows for tokens to be traded against each other. All transactions in tokens, such as for transfers or changes to a tokens database, take place on the Ethereum blockchain and are paid for in ether.[1]

ERC-20 specifies the following six mandatory standards for use in smart contracts:

  • totalSupply
  • balanceOf
  • transfer
  • transferFrom
  • approve
  • allowance

And there are three optional, albeit useful, standards:[2]

  • token name
  • symbol
  • places to the right of the decimal

As of July 12, 2018 there had been 99,228 ERC-20 tokens issued.[3] The number of tokens exploded over the next two-and-a-half years, tripling to more than 337,073 on November 23, 2020.[4]