Contract Size Checker

Measures runtime bytecode against the EIP-170 cap of 24,576 bytes, for contracts already deployed or for bytecode you have compiled but not shipped. Passing that limit is not a warning — the deployment simply reverts, and it does so at deploy time rather than while you are still writing the contract, which is why headroom is worth watching before you get there. Anything within four kilobytes is flagged. It also notes the separate EIP-3860 cap of 49,152 bytes on creation code, since a contract whose runtime fits can still fail to deploy if its constructor logic is large enough, and that failure looks identical from the outside.