Upload CSV Files
Drag and drop multiple CSV files to merge. Supports files with different column structures.
Merge CSV Files Online — Combine & Join Multiple CSVs
Free browser-based CSV merger. Append rows from multiple files or join them by a key column with inner, left, right, and full outer joins. Your files never leave your device.
Your data never leaves your browser
Inner, Left, Right, Full Join
Smart column mapping
Built-in deduplication
Drop multiple CSV files here to merge
or click to browse and combine CSV files
Merge & JoinDifferent columns OKUp to 100MB
Merge Mode
Stack rows vertically from all files
Merge Options
Merge Multiple CSV Files Online
Combine CSV files with different columns, perform SQL-style joins (inner, left, right, full), and remove duplicates. Your data stays private - all processing happens in your browser.
How to Merge CSV Files Online
Combine multiple CSV files in 3 simple steps. Works with files that have different columns.
Choose Merge Mode
Select Append to stack rows vertically, or Join to combine files horizontally by key columns.
Download Merged CSV
Preview and download your combined CSV file. All processing happens locally in your browser.
Frequently Asked Questions
Is my data secure?
Absolutely. All processing happens locally in your browser using JavaScript. Your files never leave your computer and are never uploaded to any server. This makes CSV Merge the most private way to merge your CSV files.
Can I merge CSV files with different columns?
Yes! Our smart column mapping automatically handles files with different column structures. In Append mode, missing columns will be filled with empty values. In Join mode, you can merge files horizontally based on matching key columns.
What is the difference between Append and Join modes?
Append mode stacks rows vertically from all files (like SQL UNION). Join mode merges files horizontally based on matching key columns (like SQL JOIN). Join supports inner, left, right, and full outer join types.
Can I join more than 2 CSV files?
Yes! CSV Merge supports chain joining, which allows you to join multiple files in sequence. Files are joined in the order they are added: (File1 JOIN File2) JOIN File3, and so on.
Is there a file size limit?
We recommend files under 100MB each for optimal browser performance. For larger files, consider splitting them first. Since all processing happens in your browser, the actual limit depends on your device's memory.
How does duplicate removal work?
You can remove duplicates based on all columns (exact match) or a specific key column. The first occurrence is kept and subsequent duplicates are removed. This feature is available in Append mode.
About CSV MergeThe Free Online CSV File Combiner
CSV Merge lets you merge multiple CSV files into one. Whether you need to combine CSV files with different columns or join CSV files based on a common key column, our tool handles it all directly in your browser.
Append Mode
Stack rows from multiple CSV files vertically. Perfect for combining monthly reports, sales data, or files with the same structure. Smart column mapping handles different column orders.
Join Mode
Combine CSV files horizontally like SQL JOIN. Supports Inner, Left, Right, and Full Outer Join. Ideal for merging customer data with orders, or products with inventory.
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