How to find out what is inside a computer
Before you buy memory, sell a machine or file a warranty claim, you need the actual specification rather than what you remember ordering.
Short answer
Every operating system will tell you the model, the processor, the memory and the storage without any extra software. What it will not reliably tell you is the memory's speed and how many slots are free, which is the thing you usually wanted.
What you get for free
Windows. msinfo32 gives the fullest picture: model, BIOS, processor, installed and usable memory. Task Manager’s Performance tab is better for memory, because it shows the speed, the form factor and — the useful one — how many slots are used out of how many. dxdiag covers the graphics.
macOS. → About This Mac → More Info, and then System Report for detail. On Apple Silicon, memory is part of the processor package and is not upgradeable, which makes the question shorter.
Any shell:
system_profiler SPHardwareDataType # macOS
wmic memorychip get capacity,speed,devicelocator # Windows
For most questions that is the whole answer, and no download is needed.
The three questions those do not answer well
How many memory slots are free. Task Manager gives it on Windows. On a laptop it is often wrong or unavailable, and the real answer needs the manufacturer’s specification for that exact model number — some machines have memory soldered on with one free slot, some have two, some have none.
What the storage actually is. Both systems will tell you a capacity and a model string. Whether it is NVMe or SATA, and what it is capable of, usually needs looking up the model or measuring it.
Whether the machine performs like its specification. This is the one that matters most and no inventory tool answers it. A laptop with a good processor that throttles to half speed after ninety seconds is, in practice, a slower machine than its specification says.
The measurement worth taking
Load the machine steadily for five minutes and watch what the throughput does.
A healthy machine holds its speed. A thermally limited one starts fast and settles lower — and where it settles is what you actually get during any long job, which is the number that describes the machine you own rather than the one on the box.
This also detects, without any special access, the classic problems: dust in the vents, dried thermal paste, a fan that has stopped, a machine that has been on a soft surface for a year.
What software cannot see
Worth being direct about, because a lot of tools in this category imply otherwise.
Reading temperatures, fan speeds and voltages requires privileged access to platform-specific hardware interfaces: an embedded-controller driver on Windows, SMC access on Intel Macs, and something different again on Apple Silicon. A portable program that does not install a driver cannot do it.
So a report that says nothing about temperature is not incomplete — it is honest. Sustained-load testing detects throttling by its effect, which is the thing you care about anyway. For the actual sensor values, use your motherboard vendor’s utility, or powermetrics on macOS.
The programs for this
- HardwareLens writes one readable page describing the machine: what it is, how fast it measured, what is filling the folders you point it at, and anything about those numbers worth mentioning. It is written for people who are not sysadmins, and it is explicit about everything it cannot see.
- SensorDeck is the sustained-load test: one fixed, identical workload for five minutes, reporting whether the machine held its speed.
compareputs a run from before a repair next to one from after. - DevicePulse keeps a history and shouts when something jumps — a folder that grew more than a quarter since the last reading, for instance.
- PCHealth rolls many machines’ reports into one table with outlier detection, so the one bad machine out of forty is obvious.
Free while we are in preview, one file each, Windows and Mac.
If you are buying or selling
Get the model or serial number and look it up with the manufacturer. That gives the exact configuration as shipped, the memory ceiling, the number of slots, and whether it is still in warranty — which is more, and more reliable, than anything read off the running system.
Then run the sustained-load test, because a five-year-old machine that holds its speed is worth meaningfully more than one that does not, and it is not something either party can tell by looking.