Docs
Clear definitions for results and controls. Start here when you want to know exactly what A only, Intersection, or a toggle means.
Most unexpected counts come from trim, letter case, blank lines, or CSV column mode—not from the set math itself. Read Compare basics first if your overlap looks wrong before you change more options.
Not sure whether you need a quick checker or a side-by-side compare? The list checker vs list diff page walks through that choice in plain language.
Compare basics
A only, B only, intersection, union, symmetric difference, and control options.
List checker vs list diff
When a quick check is enough versus when you need a full two-list compare.
Compare text (line diff)
When you need added/removed lines in order—not set overlap.
Compare JSON (structure)
Path-level JSON differences; object key order ignored.