Clean — by Similarity API

Free CSV & Excel File Merger

Merge two CSV or Excel files in your browser. Align columns by name, keep all fields, preview and download CSV or XLSX. Free, no upload or sign-up.

File A

Drop a file or choose from your device

File B

Drop a file or choose from your device

Columns to keepRemove exact duplicate rowsAdd source filename

Need to join on a shared key?

Your data never leaves your browser

How it works

Three steps. One clean result.

Step 1

Choose two files

Open CSV or Excel exports and choose a worksheet in each workbook.

Step 2

Align your columns

Keep all columns or just shared columns. Preview the combined rows before downloading.

Step 3

Download one file

Save the merged data as CSV or Excel, with optional exact duplicate removal.

Why Clean

The details that make a difference

Keep every column

Different column orders are aligned by name. Missing fields become blank cells.

Append, not join

Stack records into one table. Use the existing Join tool to match rows on a key.

Keep your originals

Merging creates a new download; neither original file is changed.

Before

January: name,city
Ada,London

February: city,name,tier
Paris,Grace,gold

After

name,city,tier
Ada,London,
Grace,Paris,gold

Learn more

Guides for cleaning your data

Step-by-step articles on deduplicating spreadsheets, CRM imports, and vendor exports.

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.

See all guides

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Frequently asked questions

Is this tool free?

Yes. Clean is free, with no account, payment or download gate.

Is my data uploaded?

No. Processing happens in your browser. Your input is not sent to our servers, sold, shared or used for AI training. Large inputs are limited by your device’s available memory.

Can I merge CSV and Excel together?

Yes. Each input can be CSV, TSV, XLSX or XLS. Choose one worksheet per workbook.

What if the columns differ?

All columns is the default. Headers match without regard to case or outer spaces. Shared-columns mode omits other fields and shows a warning. Headerless files align by column position. Duplicate header names must be fixed before merging.

Are duplicates removed automatically?

No. Every row is kept unless you enable exact-row duplicate removal. This is not fuzzy deduplication.

Will formulas and formatting be preserved?

The new file contains displayed cell values, not formulas, charts, macros or original formatting. Formula values depend on saved results in the workbook.