List Diff
Compare Two Lists Online
Compare two lists online and see what's different, what matches, and what's unique to each side - all computed the moment you paste. Works with raw CSV and TSV files too; the best column for comparison is picked automatically.
Your lists stay completely private - everything is compared in-memory inside the browser tab with nothing transmitted anywhere. Safe for email lists, customer CSVs, IAM rosters, and anything covered by GDPR. Close the tab and the data is gone.
Find Differences, Matches, and Unique Items
Every useful comparison is computed the moment both lists are present. Results are colour-coded so you can immediately see what's unique, shared, and missing.
Five Ways To Compare Two Lists
Every list comparison question maps to one of five set operations. All five run in parallel.
Only in A
Items in List A that aren't in List B. Answers 'what's in my old list that's missing from the new one?'
Only in B
Items in List B that aren't in List A. Answers 'what got added?'
Union
Every unique item from both lists combined, duplicates removed. Useful for building a master list from two sources.
Intersection
Items that appear in both lists. The core of any list reconciliation - answers 'which records match on both sides?'
Symmetric Difference
Items in one list but not both. The opposite of intersection - reports every line that didn't match.
How To Compare Two Lists Online
Four steps. No formulas, no code, no sign-up.
Paste Or Upload List A
One item per line, or upload a CSV/TSV file. Delimiters are auto-detected and the best column is picked for you.
Paste Or Upload List B
All five set operations run in parallel as you type.
Pick Options
Toggle case sensitivity, whitespace trimming, leading-zero handling, and space normalization.
Export Or Copy
Each result pane has Copy and Download buttons. Sort, add line numbers, or export as a .txt file.
Why Compare Lists Here
Five set operations at once, entirely in the browser, with export controls spreadsheet formulas can't match.
Instant Set Operations
All five computed in parallel the moment both lists are present. No button, no mode switching.
CSV And TSV Upload
Drop a file in - delimiter auto-detected (comma, tab, semicolon, pipe) and the best column picked by a uniqueness/readability heuristic.
Private And Secure
Lists never leave the browser tab. Computed entirely client-side, safe for customer emails and internal inventory.
All Results At Once
Only-in-A, only-in-B, union, intersection, and symmetric difference shown side by side in one screen.
Matching Options
Case sensitive/insensitive, trim whitespace, normalize spaces, ignore leading zeros. Make 'Apple' and 'apple ' match when you need to.
Export Controls
Copy to clipboard or download as .txt. Sort A-Z/Z-A, prefix with line numbers, convert case.
Free, No Sign-Up
No registration, no quota, no premium tier.
What This List Comparison Tool Handles
Replaces VLOOKUP, one-off Python scripts, and Excel add-ins for any line-based dataset.
Spreadsheets And Exports
Drop a CSV straight in or paste a single column from Excel/Google Sheets. Five answers instantly, no formulas.
- Compare two Excel columns without VLOOKUP
- Reconcile CSV exports between systems
- Find rows missing from one sheet
- Cross-reference customer or SKU lists
- Audit data migrations between tools
Data And Marketing
Email lists, contact databases, audience segments. Find overlaps, isolate new subscribers, deduplicate before importing.
- Deduplicate combined email lists
- Find unsubscribes between exports
- Isolate new contacts for a campaign
- Compare CRM and mailing list records
- Merge two audience segments cleanly
Development And DevOps
Package lists, feature flags, environment variables, access control rosters. Faster than a REPL.
- npm and pip package list diffs
- Feature flag audits across environments
- IAM user and group membership diffs
- Config key comparisons across deploys
- Allowed domain or IP list reviews
Compare Lists Using Python Sets
Python's set operators (-, |, &, ^) map directly to the five operations ListDiff computes in the browser.
# Python: Compare two lists list_a = ['Apple', 'Banana', 'Cherry'] list_b = ['Banana', 'Cherry', 'Date'] only_a = set(list_a) - set(list_b) # Only in A only_b = set(list_b) - set(list_a) # Only in B union = set(list_a) | set(list_b) # Union intersection = set(list_a) & set(list_b) # Intersection symmetric = set(list_a) ^ set(list_b) # Symmetric diff
Same results without opening a REPL or writing a script. Useful when the data lives in a spreadsheet rather than a file on disk.
Compare List A and List B
Paste List A on the left and List B on the right. Both lists are compared the moment both panes have content - no Compare button, no uploads. This replaces the VLOOKUP formulas or pandas scripts you'd normally write, except the answer is on screen the instant you finish pasting.
The result is five list comparisons at once: items only in A, only in B, in both, in one but not both, and the full union. Each set operation appears in its own pane with Copy and Download buttons, so you can export exactly the subset you need.
Frequently Asked Questions
How do I compare two lists online?
Paste one list into List A and the other into List B, one item per line. All five set operations run in parallel and each result is shown in its own pane.
Can I upload a CSV or TSV file?
Yes. Drop it in and the delimiter is auto-detected (comma, tab, semicolon, pipe). The best column is picked automatically - you can override it at any time.
How do I compare two Excel columns?
Copy the column from Excel or Google Sheets and paste into List A, then do the same for List B. Or export as CSV and drop the file in. Much faster than VLOOKUP.
How do I find items that appear in both lists?
Use the Intersection result. Combine with case-insensitive matching and whitespace trimming if your data has inconsistent formatting.
Can I ignore case when comparing?
Yes. Uncheck Case Sensitive to treat 'Apple', 'APPLE', and 'apple' as the same item. Combine with whitespace trimming and leading-zero stripping for messy data.
What's the difference between Union and Symmetric Difference?
Union is every unique item from both lists combined. Symmetric Difference is only items in one list but not the other - it excludes items that appear in both.
Can it handle thousands of items?
Yes. Hash-based set operations keep it fast even with tens of thousands of items.
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