Merge CSV Files Online - Combine Multiple CSVs
Combine multiple CSV files into one with automatic header alignment
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Merge CSV FAQ
How does CSV merging work?
The tool combines multiple CSV files, aligning columns by header names. All files must have compatible column headers to merge correctly.
What if files have different columns?
The tool will only include columns that appear in all files. Missing values will be shown as empty cells.
Is my data uploaded to a server?
No. All processing happens in your browser. Your data never leaves your device.
Merge CSV Files in Your Browser
Combine multiple CSV exports into one spreadsheet-ready file without uploading data to a server. Upload several files or paste blocks separated by ---, align columns by header name, and download a single merged CSV. Useful when sales, finance, or ops teams export the same report from different systems and you need one consolidated table for Excel or Google Sheets.
How CSV Merging Works Here
Each file is parsed locally. Rows are stacked vertically; when First row is header is enabled, only the first file's header row is kept and duplicate header lines from later files are skipped. Columns are matched by position — if files have different column counts, missing cells are left empty. Optional whitespace trimming normalizes values before merge.
Typical Workflows
- Monthly Shopify + Amazon order exports → one master CSV for accounting
- Survey responses collected in separate regional files → unified dataset
- Log extracts split by day → single file for pivot tables
Limits and Tips
Very large files (hundreds of MB) may slow the browser. For mismatched headers, rename columns in each source file first or merge in a database tool. After merging, use our Remove Duplicates tool to dedupe rows by a key column.
Privacy
Parsing and merging run entirely in JavaScript in your browser. Files are never uploaded.