# 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 defragmentation is simulated, not scripted. Each pass works out which clusters to read and write from the state of the disk at that moment, so no two runs lay out the same way. Nothing here is a recorded animation played back.
- The cluster colors are sampled from the original Legend. Free, unoptimized, optimized, reading, writing and unmovable clusters use the exact palette of the Windows 98 Disk Defragmenter, down to the corner mark that flags an unmovable cluster.
- Each ordinary pass reads its clusters in green, writes them in red, then lets them settle into their resting colors, and the three phases share the pass's time. Data moved out of the way flashes green only. Pause freezes whichever phase is on screen, and Resume carries on from there.
- In Fast mode it moves at most 24 clusters per pass, the same ceiling the real utility used. Every pass is charged a seek plus per-cluster transfer time, so the rhythm drifts the way a mechanical drive does instead of ticking to a fixed beat.
- Realistic mode answers everyone who says a defrag was never this quick. Realistic moves at most 6 clusters per pass and triples every delay, so drive C's estimate is about 61 minutes rather than 13. Windows touches the disk once or twice during the run, and each time it does the defragmenter rescans the whole drive. A few files come back fragmented and the rest of the finished work is kept. The run stays finished once it reaches 100 percent.
- The four drives behave differently. C is 2 GB on an unhurried disk and takes the longest of the four to finish. D is 1 GB at a moderate pace. E is only 512 MB but sits on the slowest drive in the set, so its passes crawl while the whole run takes less time than C. F is another 2 GB volume on a quick late-90s disk and finishes fastest. Drive G is yours to set up: choose its size and speed in Settings.
- The hard-disk audio tracks the drive. Whir and clatter play at a speed set by whichever disk you picked, so a slow one grinds and a fast one skitters. The mouse clicks are the Windows 98 ones.
- It runs offline. Install it once and the whole thing, sound effects included, works with no network connection.
- It is free, carries no ads, and asks nobody to sign up.

## 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.