Clean — by Similarity API

Compare two CSV files
— see what changed

Upload two versions of the same list. Clean highlights every added, removed, changed, and unchanged row — no formulas, no sign-up, no install.

Drop file or browse

CSV, XLSX, or XLS · up to 10 MB

Drop file or browse

CSV, XLSX, or XLS · up to 10 MB

Row-by-row diff: Added · Removed · Changed · Unchanged

How It Works

How to compare two CSV files in 4 steps

Step 1

Upload

Drop your two CSV or Excel files. No signup, no install, no data stored.

Step 2

Auto-configure

Clean reads both files and recommends the comparison key and columns. You can switch methods and tune settings before running.

Step 3

Review

See what was added, removed, changed or unchanged.

Step 4

Download Results

Get a clean diff report with Added, Removed, Changed and Unchanged sheets.

Download a Sample Report

Row-by-row diff

See exactly what changed between two CSV files.

See every row that was added, removed, changed, or left untouched between the two files — all colour-coded in one place.

Why Clean

Why spreadsheets fall apart when you need to compare two files

	EXCEL / GOOGLE SHEETS	OTHER ONLINE TOOLS	Clean
Compares across multiple columns		Some
Lets you switch between fuzzy match, exact join, and diff in one tool
Tells you upfront which approach fits your two files
Works on large files (50k+ rows combined)		Time out
Browser-based — no formulas, no add-in		Some

Loved by data teams

What people say about Clean

CSV Diff

"We compare weekly funnel exports in minutes instead of an afternoon of side-by-side spreadsheets.”

Priya Ramanathan

Data Analyst · Fintech

Clean

"Replaces the INDEX/MATCH + VLOOKUP dance I used to do every time two files had to be compared.”

Marcus Bellini

Ops Lead · Wholesale Distribution

CSV Diff

"I send the diff report straight to Salesforce ops. No back-and-forth about what changed between exports.”

Hannah Vestergaard

RevOps · B2B SaaS

Learn more

Guides for matching two lists

Step-by-step articles on reconciling CRM imports, trade-show lists, and vendor exports.

CompareTwoLists Alternative (2026): Upload CSV, JSON & Instagram HTML Directly

A free CompareTwoLists.com alternative with no size cap and no modes to tick. Upload CSV, TXT, JSON or Instagram HTML/JSON files as they are and get all three lists — copy or download as CSV.

Who Doesn't Follow You Back on Instagram? Free 2026 Method

Two free ways: paste your username for an instant list with no export, or upload your Instagram JSON or HTML files to see who doesn't follow you back, your mutuals and your fans. Free, no login, no row limits.

Fuzzy Matching Two CSV Files Online in 2026: We Tested 7 Tools on 2,050 Rows

We tested 7 online tools on two CSVs with 950 known fuzzy matches across seven identity fields. Clean recovered 949 of 950 — here is why it outperformed.

How to Join Two CSV Files Online in 2026 — Not Just Stack Them Together

Most online CSV merge tools only stack files together. Here's how to actually match rows and combine columns from two CSV or Excel files — on one column or several at once.

How to Match Two Spreadsheets by Name When You Don't Have a Shared Email

When two spreadsheets don't share a common email address, matching by name is the only option — but VLOOKUP on names fails. Here's what actually works.

How to Find Overlap Between Two Email Lists Before Sending a Campaign

Sending a cold outreach campaign to existing customers is an easy mistake to make — and hard to undo. Here's how to find the overlap between two email lists before hitting send.

The Best Free Match2Lists Alternative for Fuzzy Matching Two Lists

Match2Lists starts at $95/month with no free tier. Here are the best alternatives for fuzzy matching two CSV files — including a free option that handles name variants and multi-column matching.

How to Compare Two Contact Lists Without Excel

Excel's VLOOKUP misses contacts with different name spellings or missing emails. Here's how to compare two contact lists and actually find all the overlap — no formulas required.

How to Check If Your Apollo Export Overlaps with Your Existing CRM Data

Before importing an Apollo, ZoomInfo, or Lusha export, find out how many of those contacts already exist in your CRM — and which ones are genuinely new.

How to Find Net-New Contacts from a Trade Show Lead List

Not everyone who scanned their badge at your booth is a new lead. Here's how to find out which contacts from a trade show are genuinely new before you import them to your CRM.

VLOOKUP Alternative: Fuzzy Match Two Lists When Names Don't Match

VLOOKUP returns #N/A when names are spelled differently. Here's what to use instead when you need to match two lists where the data isn't perfectly consistent.

How to Check If Contacts Are Already in Your CRM Before Importing

Every CRM deduplicates on exact email match — which means name variants slip through as new records. Here's how to actually check which contacts already exist before you import.

How to Fuzzy Match Two Lists: Trade Show Export vs CRM (No Code)

VLOOKUP misses contacts that exist under a different name or email. Here's how to fuzzy match two lists — trade show exports, enriched leads, CRM exports — to find who's already there before you create duplicates.

See all guides

NEED MORE?

Interested in deduping larger files?

Our API handles millions of rows with sub-second matching, bulk uploads, and programmatic access. Or reach out and we'll walk you through a custom solution — free of charge.

FAQ

Frequently asked questions

Is my data safe to upload?

Both files are processed in memory and deleted immediately after your session. They are never written to permanent storage, never shared, and never used for any purpose other than generating your results. You can verify this in our privacy policy.

What file formats are supported?

CSV, XLSX, and XLS. Maximum 10 MB per file. If your files are larger, contact us — we can run them via the API.

Is the reconcile tool free?

Yes. Matching two files is free — no signup, no row limits and no payment. Upload both files, preview the results and download the full file straight away.

Which file should be File A and which should be File B?

File A is the new list you want to check — a trade-show export, an Apollo or ZoomInfo download, a vendor or partner list, anything you're about to import. File B is your existing reference — your CRM export, customer database, or current contact list. The output is structured around File A: which rows in A already exist in B (matched, suppress before import) and which rows in A are net-new (safe to import). Get this backwards and the output won't make sense, so pick A = new list, B = source of truth.

Compare two CSV files— see what changed