Find the weak link in your USB-C setup.
See what the Mac port, cable, dock, adapter and device each support, what was actually negotiated, and where the connection is being limited.
One-time purchase, yours permanently. Two Macs. 14-day refund, no questions asked. macOS 14+ on Apple Silicon.
Who needs Pro
A colleague's SSD keeps dropping mid-copy and it's your problem now. Port health counters, event traces, and live power beat guessing.
Fifteen cables, none labelled. Name each cable, recognise it when it returns, and keep a history of how it performs.
One dock at work, one at home, same laptop, different behaviour. Pro shows what each dock actually negotiated, so you stop blaming the Mac.
The box said Thunderbolt 4 and 100W. Pro shows what the connection is delivering and which part is setting the limit.
Is this the cable that gave me trouble last week?
Add a cable, give it a name. WhatCable recognises it next time and builds up a timeline: when you last used it, what it negotiated, whether it has been misbehaving. Saved-cables list, summary per cable, verdict on the port card.
You bought a 40Gbps cable and the drive runs at 5.
Port, cable, and device side by side against what was actually negotiated, weak link highlighted.
The new 4K display is running at 30Hz and macOS won't say why.
Your monitor's capability vs what the link is carrying, adapter named. It only says "not the cable" when the evidence shows it.
The drive keeps dropping out, but never while you are watching.
Per-port counters that keep score when you are not there: attaches, detaches, hard resets, failed role swaps, VDO failures. Alongside them, the live power contract, the PD event log, pin-level signal routing, and liquid-detection state.
What reviewers said.
A tiny app that does one thing, does it well.
WhatCable does a fine job of analyzing the cables attached to your Mac.David Nield, Lifehacker
Finally tells you what your USB-C cables can actually do.Brady Snyder, MakeUseOf
From Pro users
Clear explanation, no corporate nonsense, and then a new version shipped almost immediately. That is honestly impressive.
The app is so good, love it.
Great software. Great support.
Simple, one-time pricing
Unlock every Pro feature on two Macs. No subscription and no recurring charge.
- Every Pro feature unlocked immediately
- Yours permanently. No subscription, no renewal.
- Works on up to 2 Macs with one key
- Your key appears on screen the moment you pay, and by email
- 14-day refund, no reason needed
- Keeps working even if we ever retire the licence server
- 30-day offline grace period, no internet needed day to day
Requires macOS 14 Sonoma or later on Apple Silicon. Download WhatCable Free first if you want to check compatibility.
Buying a licence means you accept the terms and conditions. Need more Macs? Buy additional licences, or ask about volume licensing for 10+ Macs.
Student or educator? Email [email protected] from your academic address for 50% off.
More of what Pro can see
Every one of these inspects a connection in more detail than the free app can. The full Free and Pro comparison follows below.
Cable history
Name a cable, recognise it on later connections, and keep a timeline of how it performs.
Negotiation Diagnostics
Compare the Mac port, cable and device against the live connection, with the limiting part highlighted.
Display Diagnostics
Compare the monitor's top mode with the live DisplayPort link and identify adapters in the chain.
Live power metering
Real-time watts, amps, and voltage per port. Updates every 2 seconds from the battery controller. See exactly what your cable is delivering right now.
PD contract inspector
See the full negotiated power delivery contract: active voltage and current, all available PDOs decoded with type-aware formatting, and any capability mismatches flagged.
Cable resistance estimation
Multi-point regression across power samples estimates cable resistance in milliohms. Useful for spotting worn or marginal cables before they cause problems.
Port health counters
Lifetime attach/detach events, hard resets, shorts, I2C errors, role swap stats, and FET failures per port. See how a port has been treated over its lifetime.
PD event trace
Decoded protocol-level event history per port. See attach/detach sequences, contract negotiation steps, and hard reset events as they happen.
DP Alt Mode details
Lane count, link rate, tunneled vs native, full EDID with monitor model, manufacturer, and year for any display connected over USB-C.
Raw VDO identity
Full Discover Identity VDOs from SOP and SOP', the cable plug itself. Go beyond the e-marker summary to the raw fields your cable's controller actually reported.
Liquid detection
LDCM sensor status per port. See whether the liquid contact indicator has been triggered on any port, useful for diagnosing intermittent charging faults.
Power monitor window
Dedicated SwiftUI window with live Charts showing watts and voltage over time per port. Pin it while you test a charger or cable under load.
CLI monitor mode
whatcable --monitor streams live power and cable state to your terminal. Pipe it, script it, log it.
TUI dashboard
A live full-screen terminal view of ports, power, and Thunderbolt. Three screens, updates every 2 seconds. For the SSH and tmux crowd: whatcable --dashboard.
Widget power sparkline
Desktop widget shows a power chart alongside cable status, updated periodically by macOS on its own schedule. Glance at your desktop and see charging trends without opening anything.
CC advertisement level
Rp current advertisement level with inferred CC line voltage. See what current level your port's pull-up resistor is advertising to attached devices.
What's in each tier
The free app covers everything most people need. Pro is for engineers, power users, and anyone who wants the full picture.
| Feature | Free | Pro |
|---|---|---|
| Cable identity | ||
| Cable type (active / passive / optical) | ||
| E-marker identity (VID/PID, vendor name) | ||
| Speed and power ratings from e-marker | ||
| Raw VDO identity (SOP and SOP') | ||
| Mid-session fault warnings (overcurrent, connection drops) | ||
| Cable history (named cables, per-cable timeline and verdict) | ||
| Power | ||
| Basic charger info (voltage, wattage) | ||
| Live power metering (watts, amps, volts) | ||
| PD contract details (all PDOs, active RDO) | ||
| Cable resistance estimation | ||
| CC advertisement level | ||
| Port diagnostics | ||
| Negotiation Diagnostics (Mac port / cable / device breakdown) | ||
| Display Diagnostics (monitor top mode vs link) | ||
| Connection state and orientation | ||
| Thunderbolt link info (gen, lanes, bandwidth) | ||
| Port health counters (resets, errors, FET failures) | ||
| PD event trace | ||
| DP Alt Mode details and EDID | ||
| Liquid detection sensor status | ||
| App and CLI | ||
| Menu bar app with popover | ||
| Desktop widgets (small / medium / large) | ||
JSON output (whatcable --json) | ||
| Power monitor window (live charts) | ||
CLI monitor mode (whatcable --monitor) | ||
TUI dashboard (whatcable --dashboard) | ||
| Widget power sparkline | ||
Common questions
Does this work on Intel Macs?
What macOS version do I need?
How does activation work?
Can I use one key on multiple Macs?
Is the free version still available?
What if I need a refund?
Find the limit, then fix it.
One-time purchase, yours permanently. Two Macs, every Pro diagnostic unlocked immediately, and a 14-day refund if it isn't for you.