Staaarter

Large CSV Generator

Generates a large CSV of a chosen row and column count, filled with sequential IDs, random numbers, or random words, purpose-built for load-testing a CSV parser, import pipeline, or spreadsheet tool rather than for realistic-looking sample data. A free online tool from Staaarter, right in your browser.

Runs locallyUpdated 2026-07-29
By Staaarter Team
csvgeneratortesting

Overview

Introduction

Testing how a CSV parser, import pipeline, or spreadsheet tool behaves at scale means you need a genuinely large CSV file, not a hand-typed 5-row example. This tool generates one on demand, sized exactly to your row and column counts.

It's deliberately not trying to look like realistic business data, it's optimized for speed and predictability, so you can focus on whether your downstream tool handles volume correctly.

What Is Large CSV Generator?

A bulk CSV generator: pick a row count, a column count, and a value style, and it produces a full grid instantly, entirely in your browser.

This is a distinct tool from the `random` category's Random CSV Generator, that one aims for realistic fake data (names, emails, addresses); this one aims purely at generating N rows fast for benchmarking.

How Large CSV Generator Works

A header row of `column_1` through `column_N` is generated first, then each of the requested data rows is filled in according to the chosen value style: sequential IDs, random integers, or random words drawn from a small fixed word list.

Before generating anything, the tool checks that rows × columns doesn't exceed a 200,000-cell cap, returning a clear error explaining the cap rather than freezing the tab.

When To Use Large CSV Generator

Use this when you need to verify a CSV parser or import pipeline doesn't choke, slow down unacceptably, or run out of memory on a large file.

It's also useful for quickly producing a big CSV to test scroll performance, column-width auto-sizing, or search/filter speed in a spreadsheet or data-grid UI.

Often used alongside Empty CSV Creator, Custom CSV Creator and CSV Compressor.

Features

Advantages

  • Generates thousands of rows instantly, entirely client-side, no upload or wait for a server round-trip.
  • Three distinct value styles cover different testing needs, from simple ID counting to varied-width random content.
  • A hard cell-count cap keeps the browser tab responsive even if you ask for an unreasonably large grid.

Limitations

  • Capped at 200,000 total cells per generation; larger volumes need multiple runs.
  • Generated values are placeholders, not realistic fake data, use the `random` category's Random CSV Generator if you need names, emails, or similar realistic fields.

Examples

Small sequential-ID grid

Input

rows: 3, columns: 2, style: sequential-ids

Output

column_1,column_2
id_1,id_2
id_3,id_4
id_5,id_6

IDs increment across the whole grid left-to-right, top-to-bottom, so every cell has a unique, easy-to-verify value.

Over the cell cap

Input

rows: 100000, columns: 5

Output

(error: 500,000 cells exceeds the 200,000-cell cap)

The tool refuses to generate past the cap and explains why, rather than freezing the browser tab trying.

Best Practices & Notes

Best Practices

  • Start with a smaller row count to confirm your pipeline handles the shape correctly before scaling up toward the cap.
  • Use sequential IDs when you need to verify row counts survive a round trip through your pipeline unchanged.
  • Use random numbers or words when you want to stress column-width or sorting logic with more varied content.

Developer Notes

Generation is a single synchronous nested loop bounded by the 200,000-cell cap, then serialized once via the shared `stringifyCsvGrid` helper; keeping it synchronous (rather than chunked/async) is safe specifically because the cap keeps total work small enough not to visibly block the main thread.

Large CSV Generator Use Cases

  • Load-testing a CSV import endpoint or parser library for performance regressions
  • Stress-testing a spreadsheet or data-grid UI's scroll and rendering performance
  • Producing a large fixture file for a script that needs to process "a lot of rows" without caring what's in them

Common Mistakes

  • Assuming this produces realistic-looking data, it deliberately doesn't, use Random CSV Generator in the `random` category for that.
  • Requesting a row/column combination over the 200,000-cell cap and being surprised by the refusal rather than a slow, frozen tab.

Tips

  • If you need more than 200,000 cells, generate several files and concatenate them, most parsers won't care about the source file boundary.
  • Pair with CSV Compressor afterward to see how well repetitive generated data (especially sequential IDs) compresses.

References

Frequently Asked Questions