What does EVM-compatible mean?

What is the Ethereum Virtual Machine?

The EVM is the engine inside every Ethereum node. ethereum.org describes it as a decentralised virtual environment that executes code consistently and securely across all nodes. You can think of it as a single shared computer whose every step is re-run by every node: given the same starting state and the same transactions, every node must arrive at exactly the same new state.

Smart contracts are written in languages such as Solidity, then compiled into EVM bytecode — a list of low-level instructions (opcodes) such as ADD or BALANCE. The EVM is a stack machine that works in 256-bit words, and every instruction costs gas, which is how the network prices computation.

Several independent programs implement the EVM — ethereum.org lists Py-EVM, evmone, ethereumjs-vm and revm — and other blockchains can embed the same engine. That is what makes EVM compatibility possible.

What does a chain gain by being EVM-compatible?

A new blockchain faces a chicken-and-egg problem: developers will not build without users, and users will not come without apps. Running the EVM short-circuits that. Contracts already written for Ethereum, the Solidity language, developer tools and wallets all work with little change.

Project documentation shows how far this goes. Arbitrum says it aims to be as compatible with Ethereum as possible, from its RPC interface down to its bytecode, so Ethereum developers need little new knowledge. The OP Stack aims to be EVM-equivalent with as few changes as possible. Avalanche's C-Chain is described in its documentation as an instance of the EVM that supports Geth's API and Solidity contracts. ethereum.org adds that many sidechains are EVM-compatible as well.

For users, the visible benefit is the wallet: an Ethereum address is 0x followed by 40 hexadecimal characters derived from your key, and the same key produces an address in the same format on these chains.

Does EVM-compatible mean as secure as Ethereum?

No — and this is the most important point on the page. Running the same software is different from being protected by the same validators. The table sorts common types of EVM network by where their security comes from.

Assets move between these networks over bridges, which ethereum.org warns carry smart-contract, technical and, for operator-run bridges, custody and censorship risks. See layer 1 vs layer 2 for the bigger picture.

What differs between EVM-compatible chains in practice?

Compatible is not identical. The projects' own documentation lists differences developers and users notice:

• Fees. On Arbitrum, fees combine execution costs with a charge for posting data to the parent chain; OP Stack chains add an L1 data fee on top of execution gas.
• Timing. Arbitrum warns that block numbers and timestamps do not behave exactly as on Ethereum.
• Opcodes and visibility. On OP Stack chains some opcodes return different values, and there is no public mempool — only the sequencer sees pending transactions.
• Proof systems. ethereum.org notes that zero-knowledge rollups find full EVM compatibility difficult, which is why zkEVM projects exist.

How does a chain ID keep EVM networks apart?

If addresses look the same everywhere, what stops a transaction signed for one chain being copied onto another? EIP-155, created in 2016, added a chain ID to the data a wallet signs. Ethereum mainnet's chain ID is 1; other networks use their own numbers. A signature made for one chain ID will not validate on a chain with a different ID.

1. Check the network name and chain ID in your wallet before signing.

2. Confirm the recipient supports that network, not just the address format.

3. Look up the token contract on that network's block explorer, because a token on one chain is a separate contract from its namesake on another.

What mistakes do people make with EVM-compatible chains?

• Equating compatibility with Ethereum-level security. A sidechain's validators, not Ethereum's, decide what happens to your funds.
• Sending on the wrong network. Your address may be identical on several chains, but an exchange or friend may only watch one. ethereum.org notes that balances and history do not carry over between networks.
• Assuming tokens are interchangeable across chains. A bridged token depends on the bridge that minted it.
• Copying contracts without testing. Differences in fees, timestamps and opcodes can change how code behaves; developers test on the target chain first.