Data sources

Mac Sensors reads local macOS interfaces. Public system counters publish independently of optional SMC readings, so a slow or missing sensor group cannot make an old value look new.

Reading family	What it means
CPU activity	Change in CPU tick counters across observations
Memory	Named Mach VM page counts, plus total memory and swap use
Startup volume	Total and available space reported for the root filesystem
Network	Aggregate byte-rate deltas across eligible Ethernet/Wi-Fi interfaces
Storage	Aggregate byte-rate deltas from eligible block-storage drivers
SMC	Bounded, typed read-only temperature, fan, power and related keys

On the measured Mac17,9 with an M5 Pro, the current catalog contains 38 SMC readings and 14 public/derived readings after baselines are established. Another Mac may expose a different set. The first sample, counter resets, interface membership changes and sleep gaps withhold rates until there is a new baseline.

Memory categories are the named kernel counters. Their sum is not presented as Activity Monitor’s Memory Used. Aggregate storage and network rates are not per-application traffic.

CPU/GPU clocks, unqualified private GPU usage and ambiguous HID/IOReport channels are not offered in this release. An interface exposing bytes does not establish a sensor’s meaning. Unknown model/chip pairs do not receive the measured M5-specific table.

Successful typed zero values remain zero. An unchanged value can be a genuine new measurement. Failed readings disappear immediately; pending observations expire after 15 seconds. An internally frozen hardware register cannot be identified from an unchanged successful read alone.

Saved SMC identities include the model, key bytes and a semantic revision. A changed catalog order cannot retarget a saved key. Source layout, labels and build numbers are not used as measurement identity.