ABI Diff Tool

Compares two ABIs by full signature, since that is what determines the selector, and separates additions from removals from mutability changes. The case it exists to catch is a function that keeps its name while its parameters change: anything compiled against the old ABI then sends calldata for a selector that no longer exists, and the call reverts with no reason attached, which is the worst kind of change to ship quietly. Mutability is compared separately because a signature can survive intact while a view becomes a write. Renaming a parameter is deliberately invisible here, since it changes nothing about what callers send. Accepts JSON ABIs or plain signature lists and runs entirely in the page.