What is Call Data in Ethereum?

Call data is a memory log in an Ethereum Smart Contract that allows external data to be stored on the Ethereum blockchain in an immutable way.

It is cheaper to store data as “call data” on Ethereum because it does not interact with the Ethereum’s state. Since it does not introduce any state changes on Ethereum, it can store immutable data without having to pay high gas fees.

Call data is always present on the blockchain as a part of its history logs.


It is generally used by Optimistic Rollups to store their rollup blocks on Ethereum. This helps them keep the transactions on Ethereum but also at the moment do not have to pay high gas fees which would be needed to process each transaction on it.

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