CallStatic

CallStatic is a term used in Ethereum development, most commonly in the ethers.js library, describing a way to simulate a contract function call without changing blockchain state.

In Ethereum, interactions with contracts can be divided into state-changing transactions and read-only calls. The EVM also provides the staticcall opcode, which enforces non-state-changing execution. CallStatic builds on this idea by offering a high-level method that runs the same function as a transaction but as a local, read-only simulation. It uses the current blockchain state from a provider to determine what a real transaction would return, without broadcasting a transaction or spending gas.

How it works: calling a function via CallStatic executes the function in a non-mutating context and returns the function’s return value as if the transaction had succeeded. If the underlying function would revert, the CallStatic call rejects with an error that includes the revert reason. Because it does not modify state, there are no gas costs and no on-chain changes.

Differences from a normal transaction: a CallStatic call does not alter contract state and does not create a transaction on the network. It is primarily used to preflight or validate outcomes, test logic paths, or determine return values before issuing a real transaction.

Limitations and caveats: results depend on the current on-chain state and the environment provided by the connected node. Non-deterministic elements, recent state changes, or differences between nodes can affect the outcome. CallStatic cannot capture effects that would only occur on-chain, such as emitted events from a state-changing transaction.

Examples of use include checking the return value of a transfer function or verifying whether a function would revert before sending a live transaction. See also staticcall and read-only calls in contract interaction libraries.