PortCheck, answered.

Requirements. macOS 13 Ventura or later, on an Apple Silicon Mac.

Installing. Download the zip, double-click it, and drag PortCheck to your Applications folder. The first time you open it, macOS may ask whether you're sure, because it arrived from the internet. That's normal — it's the standard question, not a warning about the app.

First run. PortCheck checks everything as soon as it opens. That takes a few seconds.

Every socket with something plugged into it shows four separate facts. They're kept apart on purpose, because they usually get sold to you as one.

Socket can do. What the port itself is rated for. PortCheck learns this from when the socket is empty, because a busy socket reports the agreed link rather than its ceiling.

Cable. Read from the e-marker chip inside the cable.

Link agreed. What your Mac and the connected device negotiated between them. Checked three times before it's reported.

Measured. What actually moves through it, once you've run a speed test.

Underneath the measured figure is a plain verdict: whether the link is the limit, or the drive is. That's the answer most people are looking for.

Why does my drive say "health not enabled"?

Temperature, wear and error counts come from a free open-source tool called smartmontools. PortCheck can't include it, because its licence doesn't allow bundling into paid software. Installing it takes about a minute:

1. In PortCheck, click Copy the install command.
2. Open Terminal — hold Command, press Space, type terminal, press Return.
3. Paste, press Return, and wait.
4. Back in PortCheck, click Refresh.

If Terminal says command not found: brew, you need Homebrew first. It's free and widely used: brew.sh

Why does one of my drives say "this drive will not report"?

Some external drives sit behind a bridge chip that doesn't pass health requests through — common on cheaper USB enclosures and older desktop drives. Nothing PortCheck, or any tool on any platform, can do about a drive that refuses to report. Everything else about that drive still works. Thunderbolt enclosures almost always report properly; plain USB enclosures are a lottery.

Why does a socket say "free" when there's a cable in it?

PortCheck reports what the Thunderbolt system sees. A monitor over DisplayPort, or a phone charging, occupies the socket without appearing as a Thunderbolt device. When PortCheck can see a cable in a socket with no data device on it, it says display or charging rather than free.

Why do I have fewer sockets listed than my Mac has ports?

Only Thunderbolt ports are listed. Plain USB ports — including the front ports on some Mac Studio models — don't appear as sockets. A drive on one of those still shows in the Drives section, flagged as a USB connection rather than Thunderbolt.

Does PortCheck slow my Mac down?

No. A check reads information the system already has — a few seconds, and it doesn't write to your drives. The speed test is the exception: it writes a temporary file, reads it back, and deletes it. That's deliberate, and it's the only way to measure real throughput.

Temperature. Read directly from the drive. Colour coded: green below 45 °C, neutral to 57, amber to 69, red above 70. Warm is not the same as failing — most drives are rated well above 70 °C. What matters more is a drive climbing over time, which the History window shows.

Life used. How much of the drive's rated write endurance has been consumed. Below 10 percent after several years is normal.

Errors. Media errors, reallocated sectors and CRC errors. Any of these above zero is worth attention. CRC errors in particular point at the cable rather than the drive.

Health. The drive's own verdict on itself. If this is anything other than passed, back the drive up now and stop using it for anything important.

What it does. Writes a file to the volume you choose, reads it back with the disk cache stepped around, then deletes it.

Why it steps around the cache. A file that's just been written is sitting in memory — reading it back gives you the speed of your RAM, not your drive. Figures above 8,000 MB/s are impossible over any external connection, and PortCheck refuses them rather than showing a number that can't be true.

Test size. Eight gigabytes by default. Bigger is slower but harder for memory to flatter. Change it in the gear menu.

Results are kept per drive. Testing one drive doesn't clear another's result — each shows the date it was measured.

Write speeds can look low if you've run several tests in a row. Consumer drives absorb writes into a fast cache and slow once it fills. Give the drive a few minutes and test again; read speeds aren't affected.

Is it safe? It writes one temporary file and deletes it. Don't run it on a volume that's nearly full.

Cables and sockets

Better USB-C cables carry a chip that describes them; PortCheck reads it and ties it to the socket the cable is in. Two identical cables show separately because they're in different sockets — the only way to tell them apart. A cable with no chip stays anonymous, which is itself worth knowing. Click Name to label a cable; the name is tied to cable and socket, so moving it shows as unnamed elsewhere — that's how you know it moved. If a socket's ceiling says "unknown", unplug it briefly and click Refresh. "Link unstable" means the socket reported different speeds across three samples — reconnect, then try a different cable, then a different socket.

Everything it records stays in one folder on your Mac:

You can open that folder from the gear menu. Delete it and PortCheck starts fresh. It also keeps a rolling history of your checks there, which trims itself and won't grow without limit — turn on automatic checking in the gear menu and a drive slowly running hotter will show itself before it strands you.

The app won't open

If macOS says it can't verify the app, the download was likely incomplete or altered. Download the zip again and unzip it fresh rather than reusing the old copy.

It shows no sockets at all

PortCheck reads Thunderbolt information from macOS. If nothing appears, restart the Mac and try again. If it still shows nothing, send a report from the Report menu.

The speed test won't run

Usually the volume is full or read-only. Pick a different volume, or clear space.

Numbers look wrong

Send a report. The Report menu copies a plain-text summary of everything PortCheck can see, and that's almost always enough to tell you what's happening.

Use the Report menu, choose Copy to clipboard, and paste it into your email. It contains your sockets, cables, drives and any measurements — no personal files, nothing beyond your hardware.