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. It works with raw CSV and TSV files too, picking the best column to compare automatically, so there's no VLOOKUP and no script to write.
Your lists stay completely private — everything is compared in memory inside the browser tab, with nothing transmitted anywhere. That makes it safe for email lists, customer CSVs, access rosters, and anything covered by GDPR. Close the tab and the data is gone.
Five Ways To Compare Two Lists
Every list-comparison question maps to one of five set operations, and all five are computed in parallel so you never switch modes or re-run anything. Each appears in its own pane with copy and download buttons.
Only in A (A − B) — Items in List A that aren't in List B — answering "what's in my old list that's missing from the new one?"
Only in B (B − A) — Items in List B that aren't in List A — answering "what got added?"
Intersection (A ∩ B) — Items that appear in both lists — the core of any reconciliation, answering "which records match on both sides?"
Union (A ∪ B) — Every unique item from both lists combined, duplicates removed — useful for building one master list from two sources.
Symmetric Difference (A △ B) — Items in one list but not both — the opposite of intersection, reporting every line that didn't match.
Paste Columns Or Upload CSV And TSV
Lists rarely live in a tidy one-item-per-line file. Paste a column straight from Excel or Google Sheets, type items by hand, or drop in a CSV or TSV file — the delimiter is detected automatically, whether it's a comma, tab, semicolon, or pipe. There's no import wizard and no formatting step.
When a file has several columns, the best one to compare is picked for you using a heuristic that weighs uniqueness, readability, and the column header's name — and you can switch to any other column at any time. That's what turns a spreadsheet export into a list comparison without writing a VLOOKUP or a pandas script.
Matching And Output Options
Real-world lists are messy, so a few toggles decide what counts as a match and how the results come out.
Case Sensitivity. On by default. Turn it off to treat Apple, APPLE, and apple as the same item — useful for emails, usernames, and tags where case isn't meaningful.
Trim And Normalize. Trim surrounding whitespace and ignore leading zeros so "00123" and "123", or "item " and "item", line up as matches instead of near-misses.
Unique. Remove duplicates within each list before comparing, so repeated entries don't distort the counts. Turn it off to keep every occurrence.
Sort, Number, And Convert. Order any result A–Z, Z–A, or reversed, prefix lines with numbers, or convert case — then copy it or download it as a .txt file.
How To Compare Two Lists Online
Four steps — no formulas, no code, no sign-up.
- 01Add List A. Paste one item per line, paste a column from a spreadsheet, or upload a CSV/TSV file. The delimiter is auto-detected and the best column is picked for you.
- 02Add List B. Paste or upload the second list. All five set operations run in parallel the moment both sides have content — nothing is sent anywhere.
- 03Tune The Match. Toggle case sensitivity, whitespace trimming, leading-zero handling, and duplicate removal so messy data still lines up correctly.
- 04Copy Or Export. Each result pane has copy and download buttons. Sort it, add line numbers, or save any subset as a .txt file.
Why Compare Lists Here
Five set operations at once, entirely in the browser, with export controls a spreadsheet formula can't match. Eight things make it stand out:
- 01Instant Set Operations. All five — only-in-A, only-in-B, intersection, union, and symmetric difference — are computed in parallel the moment both lists have content. No Compare button, no mode switching.
- 02All Results Side By Side. Every set operation is shown at once in its own pane, so you don't re-run the comparison to answer a different question about the same two lists.
- 03CSV & TSV Upload. Drop a file in and the delimiter is auto-detected (comma, tab, semicolon, pipe), with the best column picked by a uniqueness and readability heuristic.
- 04Smart Column Picker. For multi-column files, the most list-like column is selected automatically and you can switch to any other column with one click.
- 05Flexible Matching. Case sensitivity, whitespace trimming, space normalization, and leading-zero handling let you make "Apple" and "apple " match when the data is messy.
- 06Deduplicate On The Fly. Duplicate entries within each list are removed before comparing by default, so repeated rows don't skew the counts — and it's one toggle to keep them.
- 07Export Controls. Copy to clipboard or download as .txt, sort A–Z or Z–A, prefix with line numbers, and convert case — output shaping a VLOOKUP can't do.
- 08Private & Free. Lists never leave the browser tab — computed entirely client-side, with no registration, quota, or premium tier. Safe for customer emails and internal inventory.
What This List Comparison Tool Handles
It replaces VLOOKUP, one-off scripts, and Excel add-ins for any line-based dataset. These are the situations where it helps most.
Spreadsheets & Exports
Drop a CSV straight in or paste a single column from Excel or Google Sheets and get five answers instantly, with 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 & Marketing
Email lists, contact databases, audience segments — find overlaps, isolate new subscribers, and 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 & DevOps
Package lists, feature flags, environment variables, access rosters — faster than opening 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
Find Who Doesn't Follow You Back
One of the most common reasons people compare two lists is social media: figuring out who doesn't follow you back, or who recently unfollowed you. Export your following list and your followers list — Instagram, for example, provides both in its "Download Your Information" data — paste one into each side, and the Only-in-A pane shows everyone you follow who doesn't follow you back. To catch unfollowers, compare an older followers export against a newer one: Only-in-A is who dropped you, Only-in-B is who's new.
Because the comparison runs entirely in your browser, this is far safer than the unfollower-tracker apps that ask you to log in and hand over your account — your follower lists are never uploaded or stored anywhere. Turn off case sensitivity and trim whitespace so usernames match cleanly regardless of how they were exported, and the same approach works for TikTok, X, GitHub, or any platform that lets you export a list of handles.
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, or upload a file into either side. All five set operations run in parallel and each result is shown in its own pane — there's no Compare button.
Can I upload a CSV or TSV file?
Yes. Drop it in and the delimiter is auto-detected (comma, tab, semicolon, or pipe). The best column to compare is picked automatically, and you can switch to any other column at any time.
How do I compare two Excel columns?
Copy the column from Excel or Google Sheets and paste it into List A, then do the same for List B — or export as CSV and drop the file in. It's much faster than a VLOOKUP and shows matches and differences at once.
How do I find items that appear in both lists?
Read the Intersection pane — it lists every item present in both lists. Combine it with case-insensitive matching and whitespace trimming if your data has inconsistent formatting.
How do I find what's missing or what got added?
Use the Only-in-A pane for items dropped from the second list, and Only-in-B for items that were added. Together they give you a complete before-and-after of two list versions.
Can I ignore case, spaces, or leading zeros?
Yes. Turn off Case Sensitive to treat Apple and apple as equal, enable whitespace trimming to match "item " with "item", and ignore leading zeros so "00123" equals "123" — ideal for messy exports.
Does it remove duplicates?
By default, yes — duplicate entries within each list are removed before comparing so they don't distort the counts. You can turn off the Unique option to keep every occurrence instead.
What's the difference between Union and Symmetric Difference?
Union is every unique item from both lists combined. Symmetric difference is only the items in one list but not the other — it excludes everything that appears in both.
Can I find who doesn't follow me back on Instagram?
Yes. Export your following list and your followers list (Instagram offers both under "Download Your Information"), paste following into List A and followers into List B, and the Only-in-A pane lists everyone you follow who doesn't follow you back. Compare two follower exports from different dates to spot unfollowers. It all runs in your browser, so unlike unfollower apps you never hand over your login.
Can it handle thousands of items?
Yes. The comparison uses hash-based set operations, so it stays fast even with tens of thousands of items per list.
Are my lists private?
Yes. Everything is compared in your browser — your lists are never uploaded, stored, or sent to a server. That makes it safe for customer emails, access rosters, and internal inventory.
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