CSV Merger Tool [2025]

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Merge multiple CSV files with powerful options for appending, joining, and data handling - all in your browser.

✓ In-browser Processing✓ Multiple Merge Methods✓ Flexible Configuration

Upload CSV Files

Select or drag & drop CSV or TXT files. Ensure files are plain text and use common delimiters like comma, semicolon, or tab.

Merge Options

Key Features

  • Merge multiple CSV files with two powerful methods: append (stack vertically) or join (combine based on a common field).
  • Configure how empty values, whitespace, and duplicates are handled during the merge process.
  • Preview your data at every step of the process to ensure accurate results.
  • All processing happens in your browser - your data never leaves your computer.
  • Customize output options including delimiter selection for maximum compatibility.
  • Support for large CSV files up to 10MB each.
  • No account required - completely free to use with no limits.

Merge Methods Explained

Append Mode

Stack files vertically, one after another. This is ideal when you have similar CSV files that you want to combine into one larger dataset. For example:

File 1:

name,age,city John,30,New York Alice,25,Boston

File 2:

name,age,city Bob,45,Chicago Carol,35,Seattle

Result (Append):

name,age,city John,30,New York Alice,25,Boston Bob,45,Chicago Carol,35,Seattle

Join Mode

Merge files based on a common field (join key). This is useful when you have related data spread across multiple files. For example:

File 1 (Customer Data):

customer_id,name,email 1001,John Smith,john@example.com 1002,Jane Doe,jane@example.com

File 2 (Order Data):

customer_id,order_total,date 1001,125.50,2025-01-15 1002,89.99,2025-01-20

Result (Join on customer_id):

customer_id,name,email,order_total,date 1001,John Smith,john@example.com,125.50,2025-01-15 1002,Jane Doe,jane@example.com,89.99,2025-01-20

Common Use Cases

Data Analysis

  • • Combine monthly reports
  • • Merge datasets from different sources
  • • Consolidate survey responses
  • • Prepare data for visualization

Business Operations

  • • Combine customer databases
  • • Join product and pricing data
  • • Merge inventory listings
  • • Consolidate financial records

Data Migration

  • • Prepare data for new systems
  • • Normalize data structures
  • • Combine legacy data files
  • • Clean and restructure datasets

Frequently Asked Questions

Is my data secure when using this tool?

Yes, absolutely. All processing happens entirely in your browser. Your CSV files are never uploaded to any server, ensuring that your sensitive data remains private and secure on your local device.

How should I choose between append and join modes?

Use append mode when you want to stack similar files one after another (like combining monthly reports). Use join mode when you have related data across different files that share a common identifier (like customer data and order data that both have customer IDs).

What happens if my CSV files have different columns?

The tool handles this intelligently. In append mode, you can choose to include all columns from all files (with empty values where appropriate) or use only columns from the first file. In join mode, you can merge files based on a common field while retaining all other columns.

How large can my CSV files be?

The tool supports CSV files up to 10MB each. For very large files, processing may take a bit longer depending on your device's capabilities, but all operations remain browser-based to ensure your data privacy and keep server costs low.

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