If you've ever needed to create a large Excel file for testing, benchmarking, demos, or importing data, you probably know how slow browser-based generators can become.
I built a free online tool that lets you generate Excel files with any number of rows directly in your browser:
👉 Generate Excel Files with a Specified Number of Rows
No installation. No signup. Everything runs locally.
Why build another Excel generator?
Many online generators have limitations:
Slow when generating large files
UI freezes during generation
Limited customization
Data uploaded to servers
I wanted something that could generate very large Excel files while keeping the browser responsive.
Features
The tool supports:
Generate Excel files with a specified number of rows
Custom data generation rules
Configure columns freely
Generate files containing millions of rows
Fast download after generation
Completely free
Runs entirely in your browser
Whether you're testing import performance, stress testing an application, or creating sample datasets, it can save a lot of time.
Behind the scenes: WebAssembly + Web Worker
The interesting part isn't the UI—it's the architecture.
WebAssembly for high-performance Excel generation
Instead of using a pure JavaScript implementation, the Excel generation engine is built with Go + Excelize and compiled to WebAssembly (WASM).
This provides several advantages:
Near-native execution speed
Better performance for large workbooks
Lower memory overhead than many JS libraries
Reuse of a mature Excel library
Generating hundreds of thousands or even millions of rows becomes much more practical.
Web Worker keeps the UI responsive
Heavy Excel generation shouldn't block the main thread.
The WASM module runs inside a Web Worker, so users can continue interacting with the page while the workbook is being generated.
Benefits include:
No frozen UI
Better user experience
Progress reporting
Suitable for long-running tasks
This combination of WebAssembly + Web Worker is one of the best patterns for CPU-intensive browser applications.
Why not generate Excel on the server?
Generating files directly in the browser has several benefits:
No file uploads
Better privacy
No server-side computing cost
Works even for very large datasets
Scales naturally because computation happens on the client
Modern browsers are powerful enough to handle workloads that previously required backend services.
Use cases
This tool is useful for:
Excel/xlsx file Import testing
Performance benchmarking
Database migration testing
QA testing
Sample dataset generation
Demo data creation
Try it
If you're looking for a free online Excel generator that can create large workbooks quickly, give it a try:
👉 free online Excel generator that can create large workbooks quickly
I'm also interested in hearing how others are using WebAssembly for high-performance web applications.
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