List Comparison Tool
Compare two lists side by side to find unique items, common items, and differences. Supports case-insensitive comparison.
Runs in your browser. No data leaves your device.
Frequently Asked Questions
How does the List Comparison Tool work?
Each list is split into lines and stored in a JavaScript Set for O(1) lookups. The tool then iterates through Set A checking membership in Set B to find items unique to A, iterates Set B checking membership in A for items unique to B, and intersects both Sets to find common items. Case-insensitive mode lowercases all values before building the Sets.
What results does the comparison show?
Items only in List A, items only in List B, and items common to both lists. This makes it easy to find what was added, removed, or shared between two datasets.
Is the comparison case-sensitive?
By default, yes. You can toggle case-insensitive comparison so "Apple" and "apple" are treated as the same item.
Can I compare spreadsheet columns?
Yes. Copy a column from each spreadsheet and paste them into List A and List B (one item per line). The tool shows the differences and overlaps instantly.