DiffViewr by Bsport

DiffViewr makes quick comparisons easy right where you work. Click the toolbar button, then pick two elements on the page—such as two <ul> lists, two tables, or any repeated items. The overlay shows three groups: items only on the left, items only on the right, and items present in both. You can toggle case sensitivity, trim extra whitespace, and remove duplicates to get a clean result. Everything runs locally in your browser. There are no site-wide permissions and nothing is sent anywhere; the content script is injected only when you launch a compare. It’s handy for comparing product tables, pricing grids, lineups, and change lists without copying data into another tool.