A wallet can connect to several Ethereum-compatible networks that use similar address formats. The address alone therefore does not describe the entire transaction context. Chain ID is one of the values that distinguishes the intended network.
EIP-155 introduced chain-ID-based replay protection for the transaction format it specifies. Including the chain identity in signing helps prevent a signed transaction intended for one chain from being replayed on another that uses a different chain ID. Later transaction formats also have their own specifications; do not assume every signing operation is identical.
Separate network identity from a familiar label
A network name displayed by a wallet is a human-readable label. A token symbol is another label. Neither substitutes for checking the actual network configuration and the transaction details. A convincing name on an untrusted configuration does not make it an official network.
For an illustrative development checklist, record the intended chain, its documented chain ID, the configured endpoint, and whether the operation is a transaction or another kind of signature. Compare those details against official documentation before using a test environment.
Do not paste private keys or recovery phrases into a network-checking page. Those secrets are not required to read a public chain-ID specification. Likewise, successful replay protection does not establish that a contract, bridge, asset, or counterparty is safe.
If a wallet displays an unexpected network during signing, stop and investigate rather than treating the mismatch as cosmetic. Keep development and production configurations clearly distinguished.
Chain ID solves a specific identification problem in transaction handling. Understanding that role is more useful than treating it as a general security badge or assuming that identical-looking addresses always refer to the same network context.