⚡ Quick Actions — What do you want to do next?
How to Compare Two Lists
1. Enter Your Lists
Paste or type data into List A and List B. Drag and drop .txt or .csv files.
2. Set Options
Ignore case, trim whitespace, skip empty lines, or remove duplicates.
3. Get Results
See unique items, common items, and union. Copy, download, or view side-by-side with line numbers.
What People Use ListDiff For
Find keywords your competitor ranks for but you don't
Merge lists and find unsubscribed contacts
Find who doesn't follow you back
Compare IP whitelists or env variables across servers
Verify all records transferred between databases
Track what changed between this week and last week
FAQ
ListDiff uses a Set-based algorithm with O(n) time complexity. It normalizes each item, then uses Set operations to find unique and common items. For large datasets (10K+ lines), processing runs in a Web Worker background thread so the page stays responsive. Results include original line numbers so you can locate differences in your source data.
Yes. Web Workers handle processing and virtual scrolling renders only visible rows. 100K lines typically complete in under 2 seconds.
100% client-side. No data is sent to any server. Check the Network tab in DevTools — zero uploads during comparison.
Side-by-side view shows both lists next to each other with line numbers. Items unique to List A are highlighted in red, items unique to List B in blue. This helps you see exactly where differences are in your original data.
It exports results with the original line numbers from your source lists. Each line shows where the item appeared (e.g., "A:L42" means line 42 in List A). Useful when you need to go back and edit the original file.