CSV Merger – Append Multiple CSV Files
Append multiple CSV files into one table with stack or union columns
Append two or more CSV files into one longer table. Stack mode uses the first file’s headers and places matching values beneath them; union mode keeps every unique header found across the files and fills missing fields with empty cells.
CSV Merger combines rows in upload order. It does not match records by ID or place columns side by side. For key-based matching, use the CSV Joiner listed below.
Drop your file here or browse from your device
Accepts CSV, TSV, TXT. Maximum input: 10 MiB. Files above this hard limit are rejected before local processing.
How to Use
- Upload the first CSV, then add each additional file in the order you want its rows appended
- Choose stack to use the first file’s headers or union to keep every header
- Preview the combined rows and columns
- Download the merged CSV
Features
- Stack rows using the first file’s column set
- Union every unique header across files
- Fill missing columns with empty cells
- Preserve the order in which files were added
- Preview the combined table before downloading
Use Cases
- Append monthly exports that share the same columns
- Recombine files created by a CSV splitting workflow
- Union vendor exports whose optional columns differ
Frequently Asked Questions
Is CSV Merger free to use?
Yes. It is free to use with no signup or watermark.
Is my data private when using CSV Merger?
Absolutely. All processing happens in your browser. Your data never leaves your device.
How are columns handled when merging?
Stack mode follows the first file’s headers and leaves out columns that only exist in later files. Union mode includes every unique header and fills missing values with empty cells.
Can I merge CSV files by an ID or email column?
CSV Merger only appends rows. Use CSV Joiner for key-based matching, side-by-side columns, and inner, left, right, or full outer joins.