OSX Stats Nano

An ultra-light macOS menu bar system monitor. Pure AppKit, zero dependencies, 180 KB binary, ~1,100 lines of Swift.

What it does

Displays live CPU, Memory, GPU, and Network stats in your menu bar with minimal resource usage.

• CPU — ring gauge (green)
• Memory — ring gauge (orange)
• GPU — ring gauge (purple, hidden if unavailable)
• Network — ↓/↑ throughput text

Click the menu bar item for a detailed breakdown with core counts and live-updating values.

Feedback

• Bug reports → GitHub Issues
• Ideas & feature requests → GitHub Discussions

Why another stats app?

Most menu bar monitors are bloated — SwiftUI, Combine, third-party charting libraries, 30–100 MB of RAM just to show you a number. OSX Stats Nano is built on one principle: the monitor should never be the thing slowing you down.

• Pure AppKit, zero dependencies — no SwiftUI, no Combine, nothing beyond Apple system frameworks
• Zero-alloc draw path — widgets draw directly to CGContext; SF Symbol icons cached at init, not every frame
• Change detection — skips all redraws when your system is idle; silent when nothing changes
• Per-monitor polling — each metric polls on its own interval; GPU can be slow, network can be fast
• 180 KB binary, ~1,100 lines of Swift — small enough to read in an afternoon, easy to audit, easy to trust

Install

Download (recommended):

1. Download OSXStatsNano-x.x.x.dmg from Releases
2. Open the DMG and drag OSXStatsNano into Applications
3. Open the app

Warning

First launch: macOS will block the app since it is not notarized. To open it:

• Run in Terminal: xattr -d com.apple.quarantine /Applications/OSXStatsNano.app, or
• Go to System Settings → Privacy & Security, scroll down to find "OSXStatsNano was blocked", and click Open Anyway

On macOS Ventura+, double-clicking shows a "Move to Trash / Done" dialog with no Open option — dismiss it with Done, then follow the Privacy & Security steps above.

Build from source:

git clone https://github.com/hefeicoder/osx_stats_nano.git
cd osx_stats_nano
./run.sh

Requires macOS 13+ and Xcode.

Configuration

On first launch, a config file is created at ~/.config/osx-stats-nano/config.yaml. Edit and restart the app to apply changes.

# ── Polling intervals (seconds) ─────────────────
# Minimum: 0.5s (gpu minimum: 1.0s)
# GPU uses IOKit which is heavier — 6s recommended.

cpu_interval: 2.0      # default: 2.0
memory_interval: 2.0   # default: 2.0
gpu_interval: 6.0      # default: 6.0
network_interval: 2.0  # default: 2.0

# ── Visibility ───────────────────────────────────
# Options: true | false

show_cpu: true         # default: true
show_memory: true      # default: true
show_gpu: true         # default: true
show_network: true     # default: true

# ── Widget style ─────────────────────────────────
# Options: circle | bar | vbar

cpu_style: circle      # default: circle
memory_style: circle   # default: circle
gpu_style: circle      # default: circle

# ── Widget color ─────────────────────────────────
# Options: green | orange | blue | red | purple | yellow | pink | teal

cpu_color: green       # default: green
memory_color: orange   # default: orange
gpu_color: purple      # default: purple

# ── Icons (SF Symbol names) ──────────────────────
# Browse at: developer.apple.com/sf-symbols
# cpu:     cpu | cpu.fill | bolt | bolt.fill
# memory:  memorychip | memorychip.fill
# gpu:     display | display.fill | rectangle.3.group
# network: network | wifi | antenna.radiowaves.left.and.right

cpu_icon: cpu
memory_icon: memorychip
gpu_icon: display
network_icon: network

Architecture

Monitors (system calls)  →  StatsPoller (background timer)  →  StatsSnapshot (cache)  →  Display (widgets)

Layer	What it does
Monitors	Thin wrappers around Mach (host_processor_info, host_statistics64), BSD (getifaddrs), and IOKit (IOAccelerator)
StatsPoller	Single DispatchSourceTimer on a utility queue; each monitor fires on its own interval
StatsSnapshot	Immutable value type with isDifferent() — 1% threshold for CPU/Mem/GPU, 1 KB/s for network
StatusBarView	Custom NSView on the NSStatusItem button; rebuilds widget list once per update, draw() is zero-alloc
StatsDetailView	Pure AppKit NSStackView — built lazily via NSMenuDelegate.menuWillOpen, only on click

Project Structure

Sources/
├── main.swift                    # Entry point
├── AppDelegate.swift             # Lifecycle, wires poller → display
├── AppConfig.swift               # YAML config loader (no dependencies)
├── StatsPoller.swift             # Background polling with per-monitor intervals
├── StatsSnapshot.swift           # Immutable cache with change detection
├── StatusBarController.swift     # NSStatusItem + custom NSView
├── Monitors/
│   ├── CPUMonitor.swift          # Mach host_processor_info
│   ├── MemoryMonitor.swift       # Mach host_statistics64
│   ├── GPUMonitor.swift          # IOKit IOAccelerator
│   └── NetworkMonitor.swift      # BSD getifaddrs
├── Widgets/
│   ├── StatusBarWidget.swift        # Protocol
│   ├── PercentageBarWidget.swift    # Horizontal bar
│   ├── PercentageCircleWidget.swift # Ring gauge
│   ├── VerticalBarWidget.swift      # Vertical bar
│   ├── NetworkWidget.swift          # Stacked ↓/↑ network
│   └── TextWidget.swift             # Plain text
└── Views/
    └── StatsDetailView.swift     # Dropdown detail panel

License

MIT — see LICENSE.