Clean — by Similarity API
Join two CSV files
in seconds
Match related rows across two files on a shared column — or a combination of columns. 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
How It Works
How to join two CSV files in 4 steps
Upload
Drop your two CSV or Excel files. No signup, no install, no data stored.
Pick a join key
Clean recommends the column — or combination of columns — that links the files. You can override it.
Review
Preview the merged result and which rows did not match, before paying.
Download
Get a single file with columns from both — matched rows joined, unmatched rows flagged.
Match & merge
Match related rows across two files — on one column or several.
Bring columns from File B into File A wherever a shared column matches exactly.
Why Clean
Why most online CSV merge tools cannot actually join two files
Most tools that claim to "merge" CSV files only stack them on top of each other. Joining means matching related rows across two files on a shared column — and that's where the gap shows up.
| Capability | Basic CSV merger | Excel | General AI assistant | Clean |
|---|---|---|---|---|
| Stack files vertically | Yes | Yes | Yes | No |
| Match rows using one column | Usually no | Yes | Yes | Yes |
| Match rows using several columns | No | Requires setup | Requires detailed instructions | Yes |
| Recommend matching columns | No | No | Sometimes | Yes |
| Compare added, removed, changed rows | No | Requires setup | Yes | Yes |
| Match inconsistent names or text | No | Limited | Yes | Yes |
| Remove duplicates within one file | Sometimes exact only | Exact by default | Yes | Yes |
| No formulas required | Yes | No | Yes | Yes |
| No prompt required | Yes | Yes | No | Yes |
For a deeper walkthrough of each approach, read our full guide on joining two CSV files by column online →
Loved by data teams
What people say about Clean
"Joining two prospecting exports by company name used to take a Python script. Now I just upload and pick the columns.”
Elena Kowalski
Growth Analyst · SaaS
"Fuzzy join is the missing piece for messy spreadsheets. It handles typos and suffixes like 'Inc.' vs 'Ltd.' automatically.”
David Okafor
RevOps · Fintech
"I enriched a 12k-row lead list with our CRM owner data in one click. No broken VLOOKUPs, no deleted rows.”
Sofia Marchetti
Marketing Ops · E-commerce
Simple Pricing
Free for small files. Pay only for large Excel & CSV jobs.
Process up to 500 rows for free. Larger files are priced per run.
$0
Up to 500 rows
- Fuzzy deduplication
- Multi-column matching
- Instant download
Large File
$1.99+
501 – 100,000 rows
- Up to 3,000 rows — $1.99
- Up to 10,000 rows — $4.99
- Up to 25,000 rows — $9.99
- Up to 50,000 rows — $19.99
- Up to 100,000 rows — $29.99
Monthly Unlimited
$99.99/mo
Unlimited uploads
- Up to 10 MB per file
- Unlimited file upload / deduplication
- Priority customer support
- Cancel anytime
FAQ