Optimism Vs. Arbitrum Optimism Vs. Arbitrum

Arguably a "true" alternative to Optimism, Arbitrum comes closest to Optimism as a competitor. They're both fairly new, and they both rely on optimistic rollups. To be fair, Optimism came first. And since its rollups were open source, Arbitrum merely adopted the code and made certain improvements.

Unlike Polygon, Arbitrum and Optimism are both Layer 2 blockchains, not sidechains. Also unlike Polygon, both enjoy the advantage of being able to provide its developers with the immediate tooling inherited from Ethereum. 

So what other important differences are there between these two chains?

Well, for one, Optimism has a token (OP), whereas Arbitrum does not. (Don't worry. All signs point to "Yes, a token is coming.") 

Second, and more importantly, Optimism's transactions are all verified on-chain. Moreover, only a single round of fraud proofing is involved. Let's compare this with Arbitrum. The Optimism competitor uses multi-round fraud proofing, should any suspicious transactions be detected.

The implication is that gas prices on Optimism are restricted to Layer 1 limits. But for Arbitrum, since not all transactions occur on-chain, this isn't the case. 

Lastly (and this is pretty cool), Arbitrum doesn't rely on the Ethereum Virtual Machine (EVM). Instead, it built its own, the Arbitrum Virtual Machine, which is EVM-compatible. 

By comparison, Optimism is EVM-equivalent. Whenever Ethereum undergoes a major overhaul to its consensus algorithm, Optimism's state and that of Ethereum will move in accordance.

Optimism is currently working on becoming EVM-compatible, as Arbitrum has done. After all, doing so will provide Optimism with the same flexibility and adaptability its newer competitor enjoys.