# Arbitrum One 

By [KOURAB ](https://paragraph.com/@borahkourab) · 2023-03-27

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Arbitrum One is the name of the mainnet chain built as a layer-2 solution on Ethereum. Although technically still in mainnet beta, Arbitrum One is Arbitrum’s Rollup flagship chain. Arbitrum One has a chainID of 0xa4b1 (decimal: 42161). In the future, Arbitrum Rollup technology may be used in conjunction with other rollup chains.

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*Originally published on [KOURAB ](https://paragraph.com/@borahkourab/arbitrum-one)*