MacResourceBar

Native macOS menu bar resource monitor for CPU, RAM, temperature, disk, external disk, network totals, and per-application activity.

Download the latest DMG

MacResourceBar lives in your menu bar and opens a compact resource dashboard when you click it. It is built for quickly spotting what is using CPU, memory, disk, and network without opening Activity Monitor.

Install

1. Download MacResourceBar-1.0.dmg.
2. Open the DMG.
3. Drag MacResourceBar.app into Applications.
4. Launch it from Applications.

The current public build is ad-hoc signed because no Apple Developer ID certificate is configured yet. macOS may show a Gatekeeper warning on first launch.

Current MVP

• Menu bar status item with selectable system metrics:
  • Network download/upload
  • CPU
  • RAM
  • Disk activity
  • CPU temperature when available
  • External disk activity when available
• Left click opens the popover.
• Right click opens the context menu with launch-at-login, high refresh, show/hide, settings, and quit.
• High refresh samples totals, system metrics, and per-app data roughly every second.
• Low refresh slows total/system metrics and per-app monitoring to reduce overhead.
• Popover sparklines show recent network, CPU, RAM, and disk activity for the current app session.
• Settings window exposes persistent launch, refresh, tray metric, table filter, sort, and threshold preferences.
• Popover app table shows:
  • app icon/name
  • CPU
  • RAM
  • disk read/write
  • network down/up
• Table controls:
  • filters: All, CPU, Memory, Disk, Network
  • sort: Total, CPU, RAM, Disk, Network, Name
  • per-filter threshold picker
  • search by app name
  • Active only
  • Show helpers
• Terminating an app row asks for confirmation before sending SIGTERM.
• Helper grouping is best-effort. With Show helpers off, common Chrome, Electron, generic Helper, and WebKit/Safari helper rows are grouped under a parent app name where the process name makes that possible.

Data Sources

• NetworkTotalsMonitor: public interface counters via getifaddrs.
• NetworkProcessMonitor: launches /usr/bin/nettop and parses delta CSV output for best-effort per-process network activity.
• CPUProcessMonitor: samples per-process CPU from proc_pidinfo.
• MemoryProcessMonitor: samples resident memory from proc_pidinfo.
• DiskProcessMonitor: samples per-process disk I/O from proc_pid_rusage.
• AppResourceMonitor: merges CPU/RAM/disk/network samples into AppResourceSnapshot.
• SystemMetricsMonitor: samples CPU, memory, disk, CPU temperature, and external disk activity.
• AppSnapshotFilterState: applies filtering, grouping, sorting, and thresholding for app rows.
• MenuBarPreferences: centralizes persisted UserDefaults keys and defaults.
• MenuBarViewModel: owns menu bar state, runtime history, monitor wiring, and menu bar formatting.

Measurement Notes

• Per-app CPU is normalized to 0...100% of total machine capacity, matching the system CPU scale shown in the menu bar. It is not Activity Monitor's cores * 100 process scale.
• Total sort uses normalized activity points so RAM does not dominate CPU, disk, and network simply because memory is measured in large byte counts.
• Memory thresholds are byte counts.
• Disk and network thresholds are byte-per-second rates.
• All threshold is activity points.

Limitations

• Per-app network attribution is best-effort because macOS does not expose a stable public API for live per-application network usage.
• nettop output can vary by OS version and may omit, delay, or rename process rows.
• The first nettop frame is discarded because it is a baseline, not an interval delta.
• CPU/RAM/disk process APIs are sampled for currently visible running applications; daemons and background agents are not the main MVP target.
• Helper grouping depends on process names and bundle metadata. It is intentionally heuristic.
• CPU temperature is best-effort and may be unavailable on some Macs or macOS versions.
• GPU monitoring is not part of the MVP.

Build And Run

From this directory:

./script/build_and_run.sh --verify

The script builds the NetworkMenuMonitor Xcode scheme in Debug, launches MacResourceBar.app, and verifies that the process is running. The Codex app Run action is wired to the same script.

Package DMG

To build a Release app bundle and compressed DMG:

./script/package_dmg.sh

The script writes Release/MacResourceBar-1.0.dmg and a copied app bundle at Release/MacResourceBar.app. Public internet distribution will still need Developer ID signing and notarization to avoid Gatekeeper warnings.

Project Structure

Network app/
├── .codex/environments/environment.toml
├── script/build_and_run.sh
├── script/package_dmg.sh
├── NetworkMenuMonitor.xcodeproj/
├── NetworkMenuMonitor/
│   ├── NetworkMenuMonitorApp.swift
│   ├── AppDelegate.swift
│   ├── Models/
│   │   ├── AppResourceSnapshot.swift
│   │   └── ResourceHistorySample.swift
│   ├── Services/
│   │   ├── AppResourceMonitor.swift
│   │   ├── CPUProcessMonitor.swift
│   │   ├── DiskProcessMonitor.swift
│   │   ├── LaunchAtLoginService.swift
│   │   ├── MemoryProcessMonitor.swift
│   │   ├── NetTopProcessMonitor.swift
│   │   ├── NetworkTotalsMonitor.swift
│   │   └── SystemMetricsMonitor.swift
│   ├── Utilities/
│   │   └── ByteRateFormatter.swift
│   ├── ViewModels/
│   │   ├── AppSnapshotFilterState.swift
│   │   ├── MenuBarPreferences.swift
│   │   └── MenuBarViewModel.swift
│   └── Views/
│       ├── MenuBarPopoverView.swift
│       └── SettingsView.swift
└── README.md

Privacy

The MVP reads local system counters and process metadata on the Mac. It does not send telemetry or snapshots anywhere.