Instruments

These are not calculators that ask you to estimate something. Each one takes the literal output of a command that already exists on your Mac, parses it, and reconciles the figures inside it against the number macOS puts on screen. Where those two disagree, and on every instrument here they do, the instrument shows you which one the system treats as authoritative and why the other one exists.

Three rules hold across all five. They take real output rather than typed estimates, so the result describes your machine and not an average one. They run entirely in your browser, so nothing you paste is transmitted anywhere. And they show the arithmetic rather than only the answer, so you can check the working instead of trusting it.

The five instruments

1. 01

   Battery Health Reconciler

   Why does macOS round my battery health up?

   $ ioreg -rn AppleSmartBattery

   The three separate capacity figures the battery controller publishes, only one of which reaches the screen.

   On our test Mac Settings showed 94% on this Mac. The gauge inside the battery reported 91.49%.

   Open the Battery Health Reconciler →

2. 02

   vm_stat Decoder

   What do free, active, inactive and wired actually mean?

   $ vm_stat

   Page counts in units of the page size named in the header, read from your output and never assumed to be 4096.

   On our test Mac Converts every category to bytes and computes the compression ratio your Mac is achieving right now.

   Open the vm_stat Decoder →

3. 03

   Storage Reconciler

   Where did the missing space on my 1 TB Mac go?

   $ diskutil info disk0

   Advertised capacity against reported free space, separating the decimal-versus-binary gap from space the APFS container genuinely holds.

   On our test Mac A 1 TB drive presents 926 GiB. The shortfall splits into two unrelated causes.

   Open the Storage Reconciler →

4. 04

   Responsiveness Interpreter

   Why do calls stutter when my speed test says the connection is fine?

   $ networkQuality -s

   Idle latency against loaded latency, translated into the specific failures the gap causes for calls and page loads.

   On our test Mac This connection idles at 30 ms and collapses to 662 ms under load, a 22× rise.

   Open the Responsiveness Interpreter →

5. 05

   Core Topology Reader

   How many of my Mac’s cores are the fast ones?

   $ sysctl -a | grep hw.

   Performance and efficiency counts, cache size at every tier, and how many separate cache clusters the cores sit in.

   On our test Mac A 14-core M4 Pro is 10 performance cores and 4 efficiency cores, on separate caches.

   Open the Core Topology Reader →

How to use one

Open Terminal. It is in Applications, then Utilities, or press Command and Space and type its name. Copy the command from the instrument you want, paste it into Terminal, press Return, then select the output it prints and copy that back into the instrument. None of these commands change anything on your system; all five only read state that macOS is already publishing.

You do not need to clean the output up first. Every instrument scans for the fields it needs and ignores the rest, so pasting the entire block, including lines that look like noise, is the intended way to use it. If it cannot find what it needs, it names the missing field rather than returning a number it had to guess at.

Why each one lives inside an article

A tool that tells you your battery gauge reads 91.49% while Settings displays 94% has given you a discrepancy, not an explanation. The useful part is knowing that the controller publishes three separate capacity figures, which of them macOS chooses to display, and what the gap between them says about the cell. That is an article, not a readout, so the instrument is placed inside the article that does the explaining.

The practical effect for you is that the link on each instrument above drops you directly at the tool, with the explanation immediately above and below it. Nothing is hidden behind a scroll. The anchor lands on the instrument itself.

What happens to what you paste

Nothing. The parsing runs in JavaScript that already loaded with the page, and no instrument makes a network request at any point in its operation. Your terminal output is never sent to this site, never written to storage, and never included in analytics. It exists only in the browser tab you pasted it into, and disappears when you close it. If you want to verify that rather than take our word for it, disconnect from the network first. Every instrument still works.

This matters more than it might appear, because some of these commands print identifiers tied to your specific machine. We do not want that data, we have not built anywhere to put it, and the instruments are constructed so that receiving it is not possible.

Questions

Is any of my terminal output uploaded?

No. Every instrument parses the text in your browser using JavaScript that ships with the page. There is no form submission, no analytics event carrying your output, and no network request of any kind at parse time. You can confirm this by opening the network tab before you paste, or by disconnecting from the network entirely. The instruments still work offline.

Do the instruments work on Intel Macs?

Partly. The vm_stat Decoder and the Storage Reconciler read output that Intel Macs produce in the same format, so they work. The Core Topology Reader and the Battery Health Reconciler expect the fields Apple Silicon publishes, and will tell you the input is unrecognised rather than guess at a result.

Why is each instrument inside an article instead of on its own page?

Because the number on its own is not the useful part. Knowing that your battery gauge reads 91.49% when macOS displays 94% matters only once you know which figure the controller treats as authoritative and why the two differ. The article is where that explanation lives, so the instrument sits in it.

What happens if I paste the wrong command output?

The instrument says so and names the field it could not find. None of them will produce a result from input they did not recognise, because a confident number derived from the wrong source is worse than no number.

Do I need to install anything?

No. Every command listed here is already present on macOS, and the instruments run in any current browser. Nothing is downloaded and nothing needs permission beyond opening Terminal.

Every instrument was tested against real output from the machine described in how we test. If one returns something that looks wrong, tell us on the contact page and include the input you used.