📊 Merge Multiple Excel Files — Large Dataset Manager

A high-performance, privacy-first web application built to merge, manage, and restructure extremely large Excel datasets directly on your local machine — without relying on cloud tools or exposing sensitive business data.

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🚨 Problem Statement

Traditional spreadsheet tools like Microsoft Excel and Google Sheets struggle when handling enterprise-scale datasets. Performance degradation, crashes, and row/column limitations make large-scale data preparation inefficient and risky.

Real scenario that triggered this project:

• 7 Excel files

• Each containing ~25,000 rows × 120 columns

• Required to be merged into one master dataset

• Needed to:

  • Keep header row from the first file only
  • Remove duplicate headers from the other 6 files
  • Reorder data blocks easily (move up/down)
  • Prepare a clean dataset for downstream analysis

This volume of structured data was beyond practical limits for spreadsheet software, especially when confidentiality restrictions prevented using online tools.

💡 Solution: Build a local, browser-based data merging tool that works natively on the system — fast, secure, and purpose-built for large structured files.

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🎯 Primary Use Case

This tool is designed for professionals such as:

• Business Analysts
• Data Analysts
• Operations Teams
• Finance & Reporting Teams

Who frequently need to:

✔ Merge multiple structured Excel files ✔ Preserve a single standardized header schema ✔ Rearrange file order before final merge ✔ Work with large datasets safely offline ✔ Avoid uploading confidential company data to third-party services

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🔒 Privacy-First Architecture

All file processing happens locally in your browser. No uploads. No servers. No data leaves your machine.

This ensures compliance with internal data governance and confidentiality policies.

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🧩 Core Features

• 📂 Merge multiple Excel files into a single dataset
• 🏷 Keep header row from the first file only
• 🧹 Automatically remove redundant headers
• 🔀 Reorder file blocks before merging (move up/down)
• ⚡ Optimized for large datasets
• 💻 Runs entirely in the browser using client-side processing

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🛠 Technologies

Layer	Technology
Frontend Framework	React 19.2.3
Language	TypeScript 5.9.3
Build Tool	Vite 7.2.4
Styling	Tailwind CSS 4.1.17
Excel Processing	XLSX 0.18.5

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🚀 Getting Started

Prerequisites

• Node.js (v16 or higher)
• npm, yarn, or pnpm

Installation

git clone <repository-url>
cd Merge_multiple_excel_files
npm install

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Development

npm run dev

App runs at: http://localhost:5173

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Build for Production

npm run build

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Preview Production Build

npm run preview

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📁 Project Structure

src/
├── App.tsx           # Main application component
├── main.tsx          # Application entry point
├── index.css         # Global styles
└── utils/
    └── cn.ts         # Utility functions

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📈 Why This Tool Matters

This project transforms a manual, crash-prone spreadsheet process into a controlled, scalable data preparation workflow. It bridges the gap between spreadsheet users and full data engineering pipelines — without requiring backend infrastructure.

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🧭 Roadmap

Next major enhancements planned:

• 📄 Support for additional file formats:

  • CSV
  • TSV
  • JSON
  • More structured data types

• 🧠 Smart column validation & mismatch detection

• 📊 Basic summary statistics after merge

• 💾 Export options for multiple formats

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👨‍💼 Author Motivation

Built out of a real operational bottleneck faced during large-scale business data consolidation. The goal was simple:

Handle enterprise-sized structured data efficiently, privately, and without spreadsheet limitations.

This tool is the first step toward a broader suite of local-first data preparation utilities.