# IoTeX Chain ID
A Chain ID is a unique number assigned to different, independent IoTeX Blockchains. For example, IoTeX Mainnet chain has
Chain ID = 1, while IoTeX Testnet has
Chain ID = 2. Chain IDs in IoTeX are used for security reasons, by including it into transaction signature to prevent transaction replay attacks on different networks.
# List of IoTeX Chain ID's
All IoTeX-based blockchains should adopt this Chain ID Mechanism, but replacing
CHAIN ID with a different and unique value. All testnet, consortium and IoTeX-cloned chains are encouraged to do the same: