Open-source hardware monitoring for macOS. Lives in the menu bar.
The macOS Activity Monitor is heavy and hidden in /Applications/Utilities. iStat Menus is excellent but paid. MacStats aims for the narrow middle: a menu-bar-first system monitor that shows CPU, RAM, disk, network, battery, and top processes at a glance — and stays out of your way.
- Menu bar at-a-glance — toggle any of CPU %, CPU temperature, memory used (GB), disk I/O rate, and network rate. Each metric is a separate status item, so macOS hides them individually when the menu bar gets crowded instead of dropping the whole group.
- Dropdown detail — live readouts for CPU (user / system / idle + load average + sparkline), temperature (CPU / GPU / hottest sensor + thermal pressure), memory (pressure + swap usage), network up/down, disk R/W, battery state, and a tabbed list of top processes by CPU / RAM / Disk / Network / Energy.
- Main window — full-screen sidebar nav (Overview, CPU, GPU, Memory, Disk, Network, Battery, Temperature, Fans, Processes) with charts and a filterable / sortable process table.
- CPU detail — per-core histogram split by P-cores and E-cores via
host_processor_info+hw.perflevel*.physicalcpu, plus 1 / 5 / 15 min load averages. - GPU detail — utilization, renderer / tiler breakdown, and vRAM in use via the IOAccelerator service tree (works on Apple Silicon and discrete GPUs).
- Disk per-volume — every mounted volume listed with capacity, free space, and SMART status badge (queried through
diskutil info -plist, cached for 5 minutes). - Network detail — per-interface bytes in / out, IPv4 / IPv6 addresses, plus a Wi-Fi card with SSID / RSSI / channel / band / Tx rate via CoreWLAN, and a public-IP lookup cached for 10 minutes.
- Long-window history — every chart in the main window has a
1m / 1h / 24hswitcher backed by three downsampled rings per metric (60 samples at 1 Hz, 360 at 10 s, 1440 at 1 min). - Battery detail — cycle count, max capacity vs design (health %), voltage, current, temperature, and 30-minute history rings for charge % and signed wattage (charging vs draining).
- Fans — RPM, target, min / max per fan via a Swift SMC client (
AppleSMC,kSMCHandleYPCEvent). Fanless Macs (e.g. M-series Air) get an explanatory empty state. - Per-process insight — top 8 apps by CPU / RAM / disk I/O / network bytes / energy impact, sorted in a background actor via
libproc. Right-click to Quit or Force Kill (with a confirmation alert). - Per-process network — bytes in / out per process via a long-running streaming
nettopchild, parsed from PTY stdout. - Temperature — CPU / GPU / SOC sensors via private
IOHIDEventSystemClient; thermal pressure via publicProcessInfo.thermalState. - Low idle cost — expensive probes (process iteration, IOKit battery, volume capacity XPC, IOHID temperature, GPU stats, SMC fans, Wi-Fi info, nettop process) only run while a consumer view is open, gated by independent refcounts. With the popover and main window closed, the app samples only cheap counters on a background actor. Typical idle: around 76 MB RAM, around 0.5 % CPU.
- Stable UI — fixed-width metric slots, Apple system menu font, frozen layout while the dropdown is open (no jitter when toggling), popover closes on any outside click.
- Native — Swift 6 (strict concurrency) + SwiftUI + AppKit. No Electron, no Python, no daemons, no third-party packages.
- Zero config — no accounts, no telemetry. The only outbound call is the public-IP lookup (
api.ipify.org) used by the Wi-Fi pane; it only fires while the main window is open.
(Capture the menu bar with CPU + RAM + Disk selected, and the open dropdown, and drop PNGs here.)
- macOS 13 (Ventura) or later
- Apple Silicon (arm64) — an Intel build is possible but not yet produced
Grab the latest .app from Releases, unzip, and move to /Applications.
Because the build is not signed with an Apple Developer ID yet, Gatekeeper will refuse it on first launch. Workaround:
- Right-click
MacStats.app→ Open → Open in the dialog, or - System Settings → Privacy & Security → scroll to "MacStats was blocked" → Open Anyway.
git clone https://github.com/<you>/mac-stats.git
cd mac-stats
./Scripts/run.sh # debug build + launch
./Scripts/bundle.sh release # production .app in .build/.../MacStats.appRequirements: Xcode 15+ or the Swift 6.3 toolchain. No package dependencies.
- Launch the app — the status item appears in the menu bar.
- Click any item to open the dropdown.
- At the bottom of the dropdown, toggle CPU / Temp / RAM / Disk / Network to pick which metrics show in the menu bar. Selection persists across restarts.
- Click the window icon in the dropdown header (or
⌘0) to open the full main window. - Quit from the dropdown or press
⌘Q.
No settings window; by design.
| Domain | API | Public? |
|---|---|---|
| CPU load | host_statistics with HOST_CPU_LOAD_INFO |
yes |
| CPU per-core | host_processor_info with PROCESSOR_CPU_LOAD_INFO |
yes |
| CPU clusters | sysctlbyname("hw.perflevel0/1.physicalcpu") |
yes |
| Load average | getloadavg(3) |
yes |
| Memory | host_statistics64 with HOST_VM_INFO64 |
yes |
| Memory swap | sysctlbyname("vm.swapusage") + vm_statistics64.swapins/outs |
yes |
| Network I/O | getifaddrs + if_data |
yes |
| Network per-interface IPs | getifaddrs + getnameinfo(NI_NUMERICHOST) |
yes |
| Wi-Fi | CoreWLAN (CWWiFiClient, CWInterface) |
yes |
| Public IP | https://api.ipify.org |
external |
| Disk I/O | IOKit IOBlockStorageDriver statistics |
yes |
| Volumes | FileManager.mountedVolumeURLs + URL.resourceValues |
yes |
| SMART | /usr/sbin/diskutil info -plist /dev/diskN |
yes (CLI) |
| Battery | IOPowerSources + AppleSmartBattery registry |
yes |
| Per-process | libproc (proc_listpids, proc_pidinfo, proc_pid_rusage) |
yes |
| Per-process network | /usr/bin/nettop -P -x -J bytes_in,bytes_out (streamed via PTY) |
yes (CLI) |
| Thermal pressure | ProcessInfo.processInfo.thermalState |
yes |
| CPU / GPU temperature | IOHIDEventSystemClient (Apple vendor temperature sensors) |
private |
| GPU utilization / vRAM | IOKit IOAccelerator → PerformanceStatistics dictionary |
yes (undocumented keys) |
| Fans | AppleSMC user client + kSMCHandleYPCEvent (F<i>Ac/Mn/Mx/Tg/ID) |
private |
No SIP bypass, no kexts, no private entitlements. The temperature path uses private symbols declared via @_silgen_name; the SMC client talks to AppleSMC through the standard user client interface (same as smc CLI tools). Same approach as Stats.app and similar OSS monitors.
- No SMC voltage / current sensors. Fan RPM works (added in v0.3.0), but voltage and current SMC keys vary per chip family and aren't mapped.
- Wi-Fi SSID needs Location permission on macOS 13+. Without it the pane shows "Connected" but no SSID name.
- Public IP is the only outbound call. Disabled when the main window is closed; cached for 10 minutes when it runs.
- Not yet signed / notarized. Installation requires a Gatekeeper override (see above).
- Apple Silicon only in current releases. On Intel, the temperature, GPU, and fan panes hide themselves when their respective sensor sources return nothing.
Sources/MacStats/
├── MacStatsApp.swift # @main, AppDelegate; pkill orphan nettops on launch/quit
├── StatusBarController.swift # one NSStatusItem per metric, shared NSPopover
├── MainWindowController.swift # NSWindowController hosting the main window
├── SystemStats.swift # @MainActor ObservableObject + background sampling actor; refcounted detail/full-process/nettop tiers
├── DisplayPreferences.swift # BarMetric enum + which metrics show in the bar (UserDefaults)
├── MenuBarSnapshot.swift # frozen copy of prefs while the popover is open
├── Formatters.swift
├── ProcessKill.swift # confirm-and-kill helper used by leader rows
├── Monitors/ # one sampler per hardware domain
│ ├── CPUMonitor.swift # aggregate + per-core + load average
│ ├── MemoryMonitor.swift # VM stats + swap usage and rates
│ ├── NetworkMonitor.swift # aggregate + per-interface bytes / IPs
│ ├── WiFiMonitor.swift # CoreWLAN SSID / RSSI / channel
│ ├── DiskMonitor.swift # I/O + per-volume capacity + SMART
│ ├── BatteryMonitor.swift # power source + AppleSmartBattery registry
│ ├── ProcessMonitor.swift
│ ├── NetworkProcessMonitor.swift # spawns `nettop` via PTY
│ ├── TemperatureMonitor.swift # IOHIDEventSystemClient
│ ├── GPUMonitor.swift # IOAccelerator PerformanceStatistics
│ ├── SMCClient.swift # AppleSMC user client wrapper
│ ├── FanMonitor.swift # SMC F* keys → FanInfo[]
│ └── SamplingMath.swift # shared delta / rate helpers
└── Views/
├── SingleMetricLabel.swift # one metric in the menu bar (icon + compact value)
├── MenuBarContentView.swift # dropdown content
├── MenuBarPrefsView.swift # 3-col grid of menu bar metric checkboxes
├── TopProcessesView.swift # tabbed top processes (CPU/RAM/Disk/Network/Energy)
├── MainWindowView.swift # sidebar nav (Overview / Hardware / Activity)
├── PaneKit.swift # PaneHeader, MetricCard, AreaSpark, DualAreaSpark, CenteredSpark, HistoryRangePicker
└── Panes/
├── DashboardPane.swift # at-a-glance card grid
├── MetricPanes.swift # CPU / GPU / Memory / Disk / Network / Battery / Temperature / Fans
└── ProcessesPane.swift # full filterable / sortable process table
Resources/
└── AppIcon.icns # bundled into the .app by Scripts/bundle.sh
design_handoff_macstats_logo/ # canonical icon source (SVG + sized PNGs + README)
See CLAUDE.md (mirrored at AGENTS.md) for architecture notes, the popover-driven detail sampling design, tricky Darwin API shapes (proc_pid_rusage, ProcessIdentity), and guidance for AI agents working on the codebase.
Issues and PRs welcome. Keep it simple: this is meant to stay small.
Before opening a PR:
swift build -c releasepasses./Scripts/run.shlaunches cleanly and the menu bar behaves
No tests yet; manual verification is the bar.
- Icon design:
design_handoff_macstats_logo/— hand-authored SVG, Apple-style squircle with Liquid Glass material and three activity rings. - Inspiration: iStat Menus.
MIT. See LICENSE.