# Chain IDs

ChainId is used in various places within Midpoint to specify a target chain. Every occurrence of Chain ID must resolve to one of the following numeric values:

<table><thead><tr><th width="244">Midpoint Chain ID</th><th>Chain</th></tr></thead><tbody><tr><td>1</td><td>Ethereum</td></tr><tr><td>5</td><td>Goerli Testnet</td></tr><tr><td>10</td><td>Optimism</td></tr><tr><td>137</td><td>Polygon</td></tr><tr><td>420</td><td>Optimism Goerli Testnet</td></tr><tr><td>3141</td><td>Filecoin Hyperspace Testnet</td></tr><tr><td>42161</td><td>Arbitrum One</td></tr><tr><td>80001</td><td>Polygon Mumbai Testnet</td></tr><tr><td>421613</td><td>Arbitrum Goerli Testnet</td></tr></tbody></table>