Free tool

Why is my computer so slow?

Almost every page answering this question is published by a company selling software that claims to fix it, which is why they all arrive at the same answer. Describe what the slowness actually looks like and this ranks the real causes against it, tells you how to confirm each one yourself, and says which of them your answers have ruled out.

1. Which computer

2. What does the slowness look like

Pick every one that sounds like yours.

3. Roughly how old is it

4. What kind of storage

This is the answer that changes the result most, and it is the only one you may have to go and look up. Press Ctrl+Shift+Esc, open Performance, and read the disk heading on the left: Windows labels it SSD or HDD.

Pick at least one symptom above and the causes will rank themselves against it. Nothing is sent anywhere and there is nothing to install.

Why this ranks the causes instead of listing them

A list of fifteen tips is not an answer. It is every tip that exists, in no order, leaving the reader to work out which one applies to them, and the reason it keeps being published is that it takes no position and so can never be wrong. The useful version takes a position: on most slow machines, one cause accounts for nearly all of it, and the symptoms tell you which.

Slow to open a file but fine once it is open is a storage bottleneck. Fine when cold and slow twenty minutes later is heat. Falling apart with several browser tabs open is memory. These are not overlapping symptoms of one vague condition, they are three different machines with three different fixes, and two of the three cost nothing to confirm.

What the tool cannot do is measure anything on your computer, so it does not pretend to. There is no percentage and no confidence score, because a number nothing measured is a guess in the typeface of an observation. What it prints instead is an ordering, the reason for each place in it drawn from your own answers, and the causes those answers have eliminated. An elimination is the strongest honest claim available from symptoms alone, and it is worth more than another suggestion, because it is the thing that stops you buying the wrong part.

The six causes, in full

These are what the tool ranks against your answers. Each one is a different machine with a different fix, so the section below takes them in the order that costs least, with the steps for confirming each one on Windows, a Mac and a Chromebook.

It reads from a spinning disc: A mechanical hard drive moves a physical head to reach each piece of data. Opening an app is thousands of small scattered reads, and every one of them waits for the disc to come round, so the machine spends most of its time waiting rather than computing.One part Replace the drive with an SSD. On most laptops of this age it is one panel, one screw set and a clone of the existing drive.
It has run out of memory: When memory fills, the system parks pages of it on the drive and fetches them back on demand. Switching between apps then means waiting for storage, which is why this feels worst with several browser tabs open.One part Add memory if the machine allows it. Many laptops made since roughly 2019 have it soldered to the board and cannot be upgraded at all, so check the model before buying anything.
It is getting too hot and slowing itself down: A processor that reaches its temperature limit lowers its own clock speed to stay under it. The machine is protecting itself, which is why the slowdown arrives after a while rather than at the start and why it clears after the machine has been off.Costs nothing Clear the vents and fan intakes. On a machine more than about five years old the thermal paste between the processor and its heatsink has usually dried out and is worth replacing.
The drive has no room left to work in: An SSD needs free blocks to write into and slows markedly as it fills. Both kinds of drive also hold the swap file the system needs when memory is tight, and a full drive leaves nowhere to put it.Costs nothing Free space until there is a comfortable margin rather than a sliver. Large video files, old downloads and previous system versions are usually where it went.
Too much is running that you did not ask for: Programs that launch with the machine and keep running: updaters, sync clients, chat apps, things bundled with a printer driver. Each is small and there are usually a lot of them.Costs nothing Turn off what you do not need at startup. Nothing needs to be uninstalled to test this, and nothing needs to be bought.
The machine is genuinely past it: Nothing is broken. The work has grown and the hardware has not: a browser in 2026 asks more of a processor than the same browser asked of it when the machine was new.A buying decision Weigh what a repair or an upgrade would cost against what it buys you, before spending anything.

How to fix a slow laptop, cheapest first

Work down this list rather than across it. Everything in the first group costs nothing but time, and the point of confirming a cause before spending anything is that the two fixes further down are the ones you cannot undo by changing your mind.

Costs nothing: try these first

None of these need a purchase, and all three are reversible. If one of them is your cause, you are finished here.

It is getting too hot and slowing itself down
Clear the vents and fan intakes. On a machine more than about five years old the thermal paste between the processor and its heatsink has usually dried out and is worth replacing.
Restores the speed the machine already had. It cannot make it faster than it was when it was new.
Windows
Shut it down for an hour, then use it cold and watch when it changes. A machine that is quick for ten minutes and then is not, every time, is throttling.
Mac
Same test: cold for an hour, then use it and watch for the moment the fans come up and the speed goes down.
Chromebook
Same test. Chromebooks throttle too, and the fanless ones do it silently.
The drive has no room left to work in
Free space until there is a comfortable margin rather than a sliver. Large video files, old downloads and previous system versions are usually where it went.
Only helps if you were actually out of room. On a drive that is half empty, deleting files changes nothing at all.
Windows
Settings, System, Storage. The bar at the top is the whole answer.
Mac
Apple Menu, About This Mac, More Info, Storage.
Chromebook
Settings, Device, Storage management.
Too much is running that you did not ask for
Turn off what you do not need at startup. Nothing needs to be uninstalled to test this, and nothing needs to be bought.
Real, and usually smaller than it is sold as. This is the cause that every speed-up product leads with, because it is the one their software claims to fix.
Windows
Task Manager, Startup apps. Windows prints a startup impact rating next to each one.
Mac
System Settings, General, Login Items.
Chromebook
Extensions are the equivalent here. Check chrome://extensions and remove what you do not use.

Costs one part

Only worth doing once you have confirmed the cause, because each of these is money spent on a specific bottleneck rather than on speed in general.

It reads from a spinning disc
Replace the drive with an SSD. On most laptops of this age it is one panel, one screw set and a clone of the existing drive.
This is the only item on the list that people routinely describe as feeling like a different computer rather than a slightly faster one.
Windows
Press Ctrl+Shift+Esc for Task Manager, open Performance, and look at the disk on the left. Windows labels it SSD or HDD in the panel heading.
Mac
Apple Menu, then About This Mac, then More Info and Storage. Every Mac sold since the mid-2010s uses flash storage, so this is almost never the answer on a Mac.
It has run out of memory
Add memory if the machine allows it. Many laptops made since roughly 2019 have it soldered to the board and cannot be upgraded at all, so check the model before buying anything.
Removes the stalls when switching between apps. It does nothing for how long an app takes to open the first time, which is a storage question.
Windows
Task Manager, Performance, Memory. With your normal apps open, look at In use against the total. If it is sitting near the top, memory is the constraint.
Mac
Activity Monitor, Memory tab, and read the Memory Pressure graph at the bottom. Green means there is headroom. Yellow or red means there is not.
Chromebook
Search, then Task Manager, and sort by Memory footprint. Tabs you have not looked at in an hour are usually the bulk of it.

Costs a decision rather than a part

This is the case where the cheap fixes are an afternoon wasted, and knowing that is worth more than another suggestion.

The machine is genuinely past it
Weigh what a repair or an upgrade would cost against what it buys you, before spending anything.
Knowing this is the answer is worth something on its own: it is the case where the cheap fixes are a waste of an afternoon.
Windows
The tell is that everything is slow evenly, on flash storage, with memory that is not full and a machine that is not hot. That is the case where there is nothing left to fix.
Mac
Same tell: evenly slow, cool, not short of memory, already on flash storage.
Chromebook
On a Chromebook, check the automatic update expiry date first. Past it there are no more updates, and that decides the question rather than the speed does.

What will not help

Everything below is recommended somewhere by someone with an interest in recommending it.

Registry cleaners: Microsoft's own guidance on Windows performance lists 12 things to try and does not mention the registry once. Unused entries in it are not a measurable brake on a modern machine, and a scan reporting hundreds of problems is the product rather than a finding.
Paid speed-up and driver-updater suites: The genuinely useful things they do, clearing space and disabling startup programs, are built into Windows and free. What is left is a subscription for running them for you.
Deleting temporary files, on a drive that is half empty: Freeing space fixes a slow computer only when the machine was short of space. If the storage bar is nowhere near full, this changes nothing and you have not found the cause yet.
Defragmenting an SSD: There is no head to move and no benefit to storing a file in one piece. Windows already treats SSDs and hard drives differently, correctly, without being asked.
More memory, when memory was never the problem: Doubling the RAM in a machine that was not running out changes nothing you can feel, and it does nothing whatsoever for a mechanical drive.
Reinstalling everything, as a first move: It works for a few weeks and then the same hardware limit returns, because a reinstall does not change what the machine is. It is a real fix for a software cause and an expensive afternoon for any other kind.

What Microsoft’s own advice covers, and what it leaves out

Microsoft publishes 12 solutions for improving PC performance, and they are good advice. Install updates, scan for malware, free disk space, remove unused apps, disable startup and background apps, check the power mode, optimise the drives, watch which processes are using the machine, and restart it. All of it is worth doing and none of it costs anything.

Every one of the 12is software housekeeping. Not one of them concerns the kind of storage the machine has, how much memory is installed, or whether it is too hot to run at full speed, which are the three things that decide how fast an older computer can possibly be. That is not an oversight on Microsoft’s part. It is the boundary of what an operating system vendor can advise you to do, and it is the half this page covers.

If your machine is slowing down only once it warms up, what thermal throttling is explains the mechanism in full. If you are weighing an upgrade against a replacement, the repair or replace calculator does that arithmetic, and the computer update checker tells you whether the machine is still getting security updates at all, which is worth knowing before spending anything on it.

Frequently asked

Why is my computer so slow all of a sudden?

A change over days or weeks points at software rather than hardware, because the hardware did not change in those weeks. The usual causes are a program that started launching with the machine, a browser extension, or a drive that has quietly filled up. Hardware causes such as a mechanical drive or too little memory get gradually worse over years, not suddenly over a fortnight.

Will more RAM make my computer faster?

Only if memory was the constraint. Adding memory to a machine that was never running out changes nothing you can feel, and it does nothing at all for how long an app takes to open, which is a storage question. Check whether memory is actually full before buying any: on Windows that is Task Manager, Performance, Memory, and on a Mac it is the Memory Pressure graph in Activity Monitor.

Do PC cleaner and registry cleaner programs work?

Microsoft's own guidance on improving Windows performance lists 12 things to try and does not mention the registry once. A registry with unused entries in it is not a measurable brake on a modern machine, and the scan that reports hundreds of problems is the product rather than a diagnosis. Everything genuinely useful that these tools do, such as clearing disk space and disabling startup programs, is built into Windows and costs nothing.

How do I know if my laptop has an SSD or a hard drive?

On Windows, press Ctrl+Shift+Esc to open Task Manager, go to Performance, and look at the disk entries down the left. Windows labels each one SSD or HDD in the heading. On a Mac, every model sold since the mid-2010s uses flash storage. This is the single most useful thing to know about a slow computer, and it takes about thirty seconds to find out.

Is it worth upgrading an old laptop or should I replace it?

It depends on which cause you have. Fitting an SSD to a machine that still has a mechanical drive is the cheapest large improvement available and is usually worth it even on an old laptop. If it already has flash storage, is not short of memory and is not overheating, there is no cheap upgrade left and the honest answer is that the machine is at the end of its useful life.

Why is my laptop so slow when my desktop is fine?

Heat, most often. A laptop puts the same class of processor in a chassis with a fraction of the airflow, usually sharing one small heatsink with the graphics, so it reaches its temperature limit and lowers its own clock speed under work a desktop would absorb without noticing. The tell is timing: quick when cold, slower after fifteen or twenty minutes, back to normal the next morning. The second reason is that a laptop on battery is often deliberately running slower to save it, which is a setting rather than a fault.

Does defragmenting speed up a computer?

On a mechanical hard drive it can help a little, and Windows already does it on a schedule without being asked. On an SSD there is nothing to defragment, because there is no head to move and no benefit to storing a file in one place rather than several. Windows knows the difference and treats each kind of drive correctly on its own.