What is an address in the context of Ethereum? Generally speaking, it represents an externally owned address (EOA) or contract that can receive (destination address) or send (source address) transactions on the blockchain. Technically speaking, it is the right-most 160 bits of a Keccak hash of an Elliptic Curve Digital Signature Algorithm (ECDSA) public key.

An address is your identity on the blockchain. It announces whether the address is related to a wallet, smart contract, or transaction hash. There are two types of addresses: externally owned addresses (basically your wallet address) and contract addresses.

On Ethereum and other networks compatible with the Ethereum Virtual Machine (EVM), public addresses all share the same format: they begin with 0x, and are followed by 40 alphanumeric characters (numerals and letters), adding up to 42 characters in total. They're also not case sensitive.

This address is a number, even though it also includes alphabetical characters. This is because the hexadecimal (base 16) system used to generate the address doesn't just use numerals, like our ten-digit decimal system. Instead, the hexadecimal system uses the numerals 0–9 and the letters A–F. This means it has 16 characters at its disposal, hence the name base 16. In computer science and many programming languages, the 0x prefix is used at the start of all hex numbers to differentiate them from decimal values.

Can I use the same address for different networks?

As mentioned above, EVM-compatible networks all share the Ethereum address format. This is because they're generally 'hard forks', based heavily on Ethereum's design, or share key fundamentals. Not all are derived directly from Ethereum, though – many were developed separately and designed for compatibility. Reflecting much of the same architecture naturally lends itself to sharing address formats too.

Due to these shared characteristics, you can use MetaMask to interact with any other EVM-compatible network using the same address. This includes networks such as:

• Polygon
• BSC (BNB Chain)
• Fantom
• Avalanche (C-Chain)

The interplay of networks and tokens (particularly when it comes to ERC-20 variants of native tokens) can be complex and is not without risk, so please always do your research before sending a transaction. A network's native tokens are unlikely to be interchangeable with the (ERC-20) version that you can send and receive on a wallet, for example.

How to interact with different networks

There are some cases where you need to exercise caution when it comes to address formats:

• EVM-compatible networks with different formats. Just because a network is EVM-compatible doesn’t necessarily mean it uses an 0x address in all circumstances. The Harmony network, for example, is fully EVM-compatible, but allows users to switch between the 0x and one1 versions of their address (although the number which follows this prefix is the same). Others, like Avalanche, have multiple chains with varying levels of EVM support.
• Non-EVM-compatible networks: stay away. As flexible as MetaMask is, you cannot interact with non-EVM-compatible networks on completely different blockchains. The most obvious example would be Bitcoin, which has a completely different address format. If the blockchain has nothing or little to do with Ethereum, it is unlikely to be usable with your wallet.