I disabled Windows Prefetch to save RAM — I was actually making my PC slower

Last week, I wrote about how I disabled Windows Prefetch to free up nearly 5GB of RAM on my system. At that time, I genuinely believed I was making a smart optimization. But as several readers in the comments rightly pointed out, disabling Prefetch was a mistake. The bigger mistake was believing that high RAM usage was inherently a bad thing. So I decided to revisit my decision, re-enable Prefetch, and take a closer look at how Windows actually manages memory.

I fell for the “free up RAM” myth

I saw 85% RAM usage and panicked

My laptop has 24GB of RAM, which is plenty for the kind of work I do. For context, my previous machine only had 8GB, and it got the job done, albeit with occasional slowdowns. Yet every time I opened Task Manager on my laptop, I was a bit surprised to see Windows using 80–85% of the total RAM, even when I wasn’t actively running anything demanding.

So when I came across the idea of freeing up “Cached” memory by disabling Prefetch, the logic seemed sound. For those unfamiliar with Prefetch, it’s a Windows feature that speeds up app launches. It does this by monitoring which files and resources your app uses during startup and creating a record of that activity. It then uses this information to preload frequently used data into the unused RAM, so your apps launch quickly.

Disabling Prefetch felt like an easy win because my laptop already has an SSD, so apps open quickly anyway. By disabling Prefetch, I was freeing up memory without affecting performance, which honestly felt like a win-win. But the truth is, it wasn’t necessary. I was basically falling into the trap of assuming that lower RAM usage means better performance.

My logic behind disabling Prefetch was flawed

Unused RAM is wasted RAM

I was treating high RAM usage as a problem that needed fixing. Seeing Windows use 80-85% of the total RAM made me feel that I needed to do something about it before it got out of control. My biggest oversight here was that I was treating RAM like storage space. With storage, having more free space is generally a good thing because it gives the system more room to save files. RAM works differently. It's there to be used. Windows is designed to take advantage of whatever memory is available instead of letting it sit idle.

What I failed to appreciate was how efficiently Windows handles cached memory. Prefetch wasn’t permanently occupying RAM. It was only using otherwise idle RAM to store data that Windows predicted I’d need again. More importantly, that cached memory is highly flexible. Any time an app or the system needs that memory, Windows can quickly reclaim the cache and allocate where it’s needed.

So yes, the memory I thought I was “saving” was never truly unavailable in the first place. It was serving a useful purpose elsewhere, while still remaining available for other tasks whenever needed. So no, I wasn’t improving things by disabling Prefetch.

To be fair, my original point about SSD-equipped PCs still stands true. Modern SSDs are so fast that the performance gains from Prefetch are often less noticeable than they were in the days of mechanical hard drives. But that’s very different from saying the feature is harmful. Even if Prefetch wasn’t providing a dramatic speed boost, it wasn’t hurting performance either.

I started reading Task Manager better

The numbers that matter

I eventually realized that I had been looking at the wrong numbers in Task Manager all along. I was looking at “In Use” and “Cached” figures. What I should’ve been paying attention to is the "Committed" line. As you can see from the above image, it reads 36.3/48.6 on my system. The first number is the total amount of RAM Windows has promised to the apps and system, either through the physical RAM or pagefile space. The second number is the commit limit, which is essentially the total capacity of RAM and pagefile.

That single metric tells me almost everything I need to know about my PC’s RAM situation. As long as committed memory remains comfortably below the commit limit, Windows still has room to satisfy new memory requests. High RAM usage isn’t really a problem if the system still has enough available.

The only time I need to worry is when committed memory starts approaching that limit, because the system can no longer guarantee new memory allocations. If the committed memory ratio reaches the 90–95% limit, that’s when things start to feel a bit sluggish. In fact, by then, I probably won’t even need the Task Manager to tell me something is wrong. Windows will make it pretty obvious.

Windows also has a tool called Resource Manager if you want to understand where all that memory is going. It gives a much more detailed breakdown of memory usage, including how much is in use, on standby, modified, or truly free.