What is Windows ReadyBoost & How Does it Work?

If you have an older Windows PC that feels sluggish, you may have come across ReadyBoost – a built-in feature that promises a speed boost using nothing more than a spare USB stick. It sounds almost too good to be true, and the reality is nuanced: ReadyBoost genuinely helps in some situations and does very little in others. This guide explains what Windows ReadyBoost is, how it works, how to set it up, and – crucially – when it is actually worth using.

What is Windows ReadyBoost?

ReadyBoost is a feature introduced with Windows Vista and still present in Windows today. It allows the operating system to use the storage on a USB flash drive (or memory card) as an additional disk cache – a fast holding area for frequently used data. The idea is that reading small, scattered pieces of data from flash memory can be quicker than reading them from a slow mechanical hard drive, so keeping copies of that data on a USB stick can make the computer feel more responsive. It was designed for an era when RAM was expensive and most PCs used slow spinning hard disks.

How does ReadyBoost work?

When you enable ReadyBoost on a USB drive, Windows sets aside space on the drive and works with a feature called SuperFetch to store a cache of frequently accessed files and data there. Because a flash drive has no moving parts, it can serve up lots of small, random reads faster than a mechanical hard drive, which has to physically move its read head around the disk. So when the system needs one of those cached pieces of data, it can grab it from the USB stick’s cache instead of waiting for the hard drive. The data is also encrypted and kept in sync, so you can safely remove the drive at any time without losing anything – the computer simply falls back to the hard drive. Understanding how a flash drive works helps explain why this speed difference exists.

How to set up ReadyBoost

Enabling it takes seconds. Plug in a suitable USB drive, open File Explorer, right-click the drive and choose Properties, then select the ReadyBoost tab. Choose either “Dedicate this device to ReadyBoost” (which uses the whole drive) or “Use this device” and set how much space to allocate, then click Apply. Windows creates the cache file and starts using it. If the tab tells you the device cannot be used, the drive is not fast enough – or your system is already fast enough that ReadyBoost would not help, in which case Windows simply will not offer it.

Does ReadyBoost actually help?

This is the honest, important part. ReadyBoost can make a noticeable difference on an older PC that has a slow mechanical hard drive and limited RAM – say 4GB or less. In that situation, the flash cache genuinely speeds up the many small reads the system makes, and the computer can feel more responsive. However, on a modern PC it makes little or no difference. If your computer has a solid-state drive (SSD), that SSD is already far faster than any USB stick, so caching to a slower drive achieves nothing – and Windows will usually not even offer ReadyBoost. Likewise, if you have plenty of RAM (8GB or more), the system rarely needs the extra cache. In short: worthwhile on old, hard-drive-based machines; largely pointless on modern, SSD-based ones.

ReadyBoost requirements

For ReadyBoost to work well, the drive needs to meet a few requirements. It must be reasonably fast – Windows tests the drive and will reject one that is too slow, so a quality USB 3.0 drive is ideal. It needs enough free space; Microsoft suggests a cache of roughly one to three times the amount of RAM in your PC, so a few gigabytes is usually plenty. The drive should be dedicated to the task while in use, as running other files from it at the same time can reduce the benefit. Windows can use multiple drives for ReadyBoost at once, though one good drive is normally enough. And bear in mind the cache size limits: a FAT32-formatted drive is capped at 4GB of cache, whereas NTFS or exFAT formatting allows more. In practice, a modest, fast, dedicated USB drive with a few gigabytes free is exactly what ReadyBoost is designed for.

ReadyBoost vs upgrading RAM or an SSD

It is worth being clear-eyed about alternatives. ReadyBoost is a clever way to squeeze a little more life out of an old machine using hardware you already own, but it is a stopgap, not a transformation. If a computer is genuinely struggling, the two upgrades that make a dramatic difference are adding more RAM and, above all, replacing a mechanical hard drive with an SSD. An SSD upgrade in particular can make an old PC feel like a new one, because it is vastly faster than both a hard drive and any USB stick. ReadyBoost cannot come close to that. So the sensible way to think about it is: if you cannot or do not want to upgrade the hardware, ReadyBoost is a free, zero-risk way to gain a modest improvement on an old, hard-drive-based PC; but if you are able to add RAM or fit an SSD, that will always be the better investment. ReadyBoost buys a little time; a hardware upgrade solves the problem.

Is ReadyBoost still relevant today?

ReadyBoost is very much a product of its time. When it launched, RAM was costly and nearly every PC ran on a slow spinning hard disk, so a clever flash-based cache made real sense. Today, RAM is cheap and plentiful, and SSDs have become standard even in budget machines – and against an SSD, ReadyBoost simply has nothing to offer, which is why modern PCs usually will not enable it at all. That said, it has not vanished, and there are still plenty of older laptops and desktops in daily use that fit its ideal profile perfectly: a slow hard drive, limited memory, and a spare USB port. For those machines, and for anyone nursing an ageing computer along, ReadyBoost remains a genuinely useful, cost-free trick. It is a nice example of a feature that quietly outlived the era it was designed for, still helping the older hardware that needs it most while gracefully stepping aside on the modern kit that does not.

The pros and cons of ReadyBoost

Weighing it up simply: on the plus side, ReadyBoost is free, uses hardware you probably already have, is quick and safe to set up, and can be removed at any time with no harm done. On an old, hard-drive-based PC with little RAM it offers a real, if modest, responsiveness gain, and it carries essentially no risk – the cache is encrypted and the system falls back gracefully if the drive is removed. On the minus side, its benefit is limited and situational: it does nothing useful on modern SSD-based machines, it ties up a USB port and a drive while in use, and it is no substitute for a proper hardware upgrade. There is also a very slight consideration that using a drive constantly as cache involves a lot of small reads and writes, though the wear on a decent modern drive is negligible in practice. Overall it is a low-risk, low-cost feature with a narrow but genuine sweet spot – useful exactly where it is needed, and quietly irrelevant everywhere else.

Tips for getting the best from ReadyBoost

If you decide to try it, a few tips help you get the most out of it. Use a fast, good-quality USB drive – ideally USB 3.0 – because a slow drive gives little benefit and Windows may reject it outright; the quality of the flash and controller matters here just as it does everywhere else. Dedicate the drive to ReadyBoost rather than storing other files on it at the same time, so its speed is available for caching. Leave the drive plugged in, since ReadyBoost only helps while it is connected – a small, low-profile drive that can stay in a spare port permanently is ideal. Follow Microsoft’s guidance on cache size (around one to three times your RAM) rather than allocating far more than you need. And keep your expectations realistic: ReadyBoost smooths out an old machine, it does not turn it into a new one. Used sensibly on the right hardware, though, it is a genuinely handy way to get a little more out of a spare USB stick and an ageing PC.

Help & Support

Frequently Asked Questions

What is Windows ReadyBoost?

ReadyBoost is a Windows feature, introduced in Vista and still present today, that lets you use a USB flash drive or memory card as extra disk cache. It stores frequently used data on the fast flash drive to help speed up a PC, particularly one with a slow mechanical hard drive.

How does ReadyBoost work?

When enabled, Windows sets aside space on the USB drive and, working with SuperFetch, keeps a cache of frequently accessed data there. Because flash serves small random reads faster than a spinning hard drive, the system can fetch that data from the drive’s cache. The cache is encrypted and synced, so you can remove the drive safely at any time.

How do I set up ReadyBoost?

Plug in a suitable USB drive, right-click it in File Explorer, choose Properties, and open the ReadyBoost tab. Select “Dedicate this device to ReadyBoost” or set how much space to use, then click Apply. If Windows says the device cannot be used, it is either too slow or your PC is already fast enough not to need it.

Does ReadyBoost actually make a difference?

It can noticeably help an older PC with a slow mechanical hard drive and limited RAM (4GB or less). On a modern PC with an SSD or plenty of RAM it makes little or no difference, because an SSD is already much faster than any USB drive, and Windows usually will not even offer it.

What kind of USB drive do I need for ReadyBoost?

A reasonably fast drive – a quality USB 3.0 drive is ideal, and Windows will reject one that is too slow. You need a few gigabytes free (Microsoft suggests a cache of one to three times your RAM), and NTFS or exFAT formatting allows a larger cache than FAT32’s 4GB limit.

Is ReadyBoost better than adding RAM or an SSD?

No. ReadyBoost is a free stopgap for old hardware you already own, but adding RAM and especially fitting an SSD make a far bigger difference – an SSD can make an old PC feel new. Use ReadyBoost if you cannot upgrade; otherwise a hardware upgrade is the better investment.

Conclusion

Windows ReadyBoost is a neat, cost-free feature that turns a spare USB stick into extra cache to speed up a PC – but its usefulness depends entirely on your hardware. On an older computer with a slow mechanical hard drive and limited RAM, it can give a genuine, welcome boost using a drive you already own. On a modern machine with an SSD or plenty of memory, it does little or nothing, and Windows will usually not offer it. If your PC is struggling and you can upgrade, more RAM or an SSD will always beat ReadyBoost; if you cannot, it is a risk-free trick worth trying with a fast USB drive. If you would like quick, quality branded USB drives – for ReadyBoost or anything else – our team is happy to help.