# Defrag98: Windows 98 Disk Defrag Simulator

> A free, browser-based recreation of the Microsoft Windows 98 Disk
> Defragmenter, built by Dennis Morello. Pick one of four virtual drives, or
> size your own, and watch the cluster grid consolidate to the sound of a late-90s hard disk. The
> defragmentation is simulated rather than scripted, so no two runs look alike.
> It installs as an offline web app, is free, carries no ads, and never touches
> a real file on the visitor's device.

Last updated: 2026-10-01

## Primary

- [Defrag98](https://defrag98.com): The live simulator. Pick a drive
  (C, D, E, or F, or size your own as Drive G) and watch it defragment, just
  like in 1998.
- [How it works](https://defrag98.com/how-it-works): Primary technical
  reference for the simulation: the cluster grid, the three moves each pass can
  make, the frontier, the timing model behind the four drives, where it
  departs from the real utility, why Windows 98 kept restarting a defrag, and
  whether a Windows 11 PC still needs defragmenting.
- [Full description](https://defrag98.com/llms-full.txt): Complete reference,
  including how the simulation works, the four drives, and answers to common
  questions.

## Support

- [Buy Me a Coffee](https://www.buymeacoffee.com/morellodev): The only way to
  support Defrag98. Optional; a coffee costs 3 euros.

## What makes it different from other defrag simulators

- The cluster shuffle is computed each pass from the current state of the disk,
  not replayed from a recorded animation.
- The cluster palette is sampled from the real Windows 98 Disk Defragmenter
  legend, including the corner mark on unmovable clusters.
- Each ordinary pass shows green reads before red writes, then settled colors.
  Evictions flash green only. The phases share the pass's time budget, and
  Pause freezes the current phase.
- In Fast mode it moves at most 24 clusters per pass, the ceiling the original
  utility used, and charges each pass a seek plus per-cluster transfer time, so
  the pace varies the way a mechanical drive does.
- Realistic mode moves at most 6 clusters per pass and triples every delay, and
  Windows touches the disk once or twice during the run. The defragmenter
  rescans the whole drive, a few files come back fragmented and the rest of the
  finished work is kept. The run finishes and stays finished.
- The hard-disk audio plays at a rate set by the drive you selected, so a slow
  disk grinds and a fast one skitters.
- It works with no network connection once installed.

## Also known as

- Fake defrag, retro defrag, defrag screensaver, defrag emulator, defrag game,
  Windows 98 simulator, Disk Defragmenter online. They all mean this site.

## About

- [Author](https://morello.dev/): Dennis Morello, creator and maintainer, a
  software engineer based in Milan, Italy.
- [Build notes](https://morello.dev/blog/windows-98-defrag-simulator): How the
  simulator was built.
- [Changelog](https://defrag98.com/changelog): Release history, styled as a
  Windows 98 CHANGELOG.TXT in Notepad.
- [Privacy](https://defrag98.com/privacy): What the site stores and measures.
- [Sitemap](https://defrag98.com/sitemap-index.xml): Crawlable URL list.

## Notes

- This is a nostalgia simulator, not a real disk utility. It does not access
  or modify any files on the visitor's device.
- Not affiliated with or endorsed by Microsoft. "Windows 98" is used to
  describe the software being recreated.