🧩 Multi-File Concatenator

CSV Merge & Combiner

Consolidate multiple monthly reports, export logs, or split datasets into one unified master spreadsheet file.

Drag & drop multiple CSV files here, or browse

Select 2 or more files to combine into a master table

0 merged rows0 columns

Master Table Preview (First 50 Rows)

What is a CSV Merge & Combiner?

A CSV merge utility is a tabular data processing tool that synthesizes multiple delimited spreadsheet files into a single, cohesive master dataset. It supports both vertical row unioning (appending recurring monthly files or distributed server logs) and horizontal relational joins (matching records across disparate files using a primary key identifier).

How to merge multiple CSV files online

  1. Upload your files: Select multiple .csv files or drag them into the upload dropzone.
  2. Choose merge strategy: Use Append Rows to stack files on top of each other, or Join on Common Key to enrich records side-by-side.
  3. Verify column mappings: Check the live preview to confirm all column headers and data types align properly.
  4. Export your combined dataset: Download the merged file as a unified CSV or an Excel spreadsheet workbook.

Need to sanitize your combined dataset? Use our CSV Cleaner & Deduplicator, or inspect individual entries with our Spreadsheet Table Viewer.

Frequently asked questions

How does vertical row appending (Union) work?

When you select "Append Rows", the merger aligns data by matching column header names across all uploaded files. New columns found in later files are added automatically, and missing cells are filled with blanks.

How does key-based horizontal joining work?

In "Join on Common Key" mode, the merger performs a database-style merge (similar to Excel VLOOKUP or SQL LEFT JOIN). It matches rows that share the same key value (such as ID or Email) and merges their attributes into a single wide row.

How many files can I merge simultaneously?

You can upload dozens of files at once. The tool processes each file in sequence inside your browser memory.

Is my data secure and private?

Yes. Every calculation and merge operation runs 100% locally on your device in JavaScript. No files or records are sent to external servers.

Can I export the merged dataset as an Excel (.xlsx) file?

Yes. You can download the consolidated table as a standard CSV or a formatted Microsoft Excel (.xlsx) workbook.

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