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Solidity Support

Arbitrum Nitro chains are Ethereum compatible, and therefore allow you to trustlessly deploy Solidity contracts (as well as Vyper or any other language that compiles to EVM bytecode).

Differences from Solidity on Ethereum

Although Arbitrum supports Solidity code, there are differences in the effects of a few operations, including language features that don't make much sense in the Layer 2 context:

  • blockhash(x) returns a cryptographically insecure, pseudo-random hash for x within the range block.number - 256 <= x < block.number. If x is outside of this range, blockhash(x) will return 0. This includes blockhash(block.number), which always returns 0 just like on Ethereum. The hashes returned do not come from L1.
  • block.coinbase returns the designated internal address 0xA4b000000000000000000073657175656e636572 if the message was posted by a Sequencer. It it's a delayed message, it returns the address of the delayed message's poster (Note: the handling of delayed message's block.coinbase will likely be changed in ArbOS v11).
  • block.difficulty and block.prevrandao returns the constant 1
  • block.number return an "estimate" of the L1 block number at which the Sequencer received the transaction (see Block Numbers and Time)
  • msg.sender works the same way it does on Ethereum for normal L2-to-L2 transactions; for L1-to-L2 "retryable ticket" transactions, it will return the L2 address alias of the L1 contract that triggered the message. See retryable ticket address aliasing for more.
  • OPCODE push0 is not yet supported, but will soon be available. This means that solidity version 0.8.20 or higher can only be used with an evm-version lower than the default shanghai (see instructions here to change that parameter in solc, or here to set the solidity or evmVersion configuration parameters in hardhat). Versions up to 0.8.19 (included) are fully compatible.