NVMeter

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A native macOS menu-bar SMART monitor for internal and external NVMe/SATA SSDs. Free and open source forever for personal use.

Website: https://hualiu77.github.io/NVMeter/

Install

1. Download the latest NVMeter-x.y.z.dmg (signed with Developer ID and notarized by Apple — no Gatekeeper warnings).
2. Open the DMG, drag NVMeter.app into the Applications folder.
3. Launch from Spotlight (⌘+Space → NVMeter). A chip icon appears in your menu bar.

Requires macOS 14 Sonoma or later on an Apple Silicon Mac.

Why

macOS has no first-party way to see your SSDs' temperature, wear, or remaining spare. smartctl does the heavy lifting but is CLI-only, and most GUI options on the Mac are closed-source or unmaintained. NVMeter is a thin, native SwiftUI menu-bar app on top of smartctl that:

• Shows the hottest drive's temperature in your menu bar at all times.
• Reads full SMART/NVMe health for internal SSDs and external USB / Thunderbolt enclosures.
• Records a local history (SQLite) so you can spot trends.
• Warns you when a drive crosses temperature or wear thresholds — no cloud, no telemetry.
• Benchmarks read/write speed with a temperature overlay — the one thing pure speed tools can't do — so it can explain SLC-cache vs thermal slowdowns.

Project values

1. Personal use is free, forever. The core monitoring app is AGPL-3.0 and will not be moved behind a paywall. See BUSINESS.md for the open-core boundary.
2. The community owns the device-compatibility database. USB / Thunderbolt bridge-chip pass-through quirks live in a separate public-domain (CC0) repository: NVMeter-drivedb. Contributing a new enclosure is one YAML file, no Swift required.
3. No telemetry, ever, in the open-source build.

Status

Current release: v0.3.0 — disk speed test with temperature overlay.

Layer	State
smartctl JSON wrapper	✅
Health scoring (temperature / wear / spare / media errors)	✅
SQLite history store (GRDB)	✅
Menu-bar SwiftUI shell with brand mark	✅
Per-drive capacity bar, brand, connection, dock-name detection	✅
Full SMART detail view (pre-fail / life-span groups)	✅
24h / 7d / 30d trend charts (Swift Charts)	✅
Threshold-based system notifications	✅
Disk speed test (CrystalDiskMark-style) with temperature overlay + link-ceiling comparison	✅
Speed-drop attribution (thermal-throttle vs SLC-cache, read off the temperature track)	✅
Wear-trend projection (local linear extrapolation of stored history → "reaches N% around …")	✅
Configurable menu-bar metric (temperature / wear / health dot)	✅
Bridge-DB loader + runtime -d auto-retry	✅
USB-SATA -d probe ladder — auto-tries every translation mode to unlock cooperative bridges, no kext	✅
Contribution flywheel — probe-unlocked enclosures offer a one-click drivedb PR with the working flags	✅
Sparkle auto-update	✅
Signed (Developer ID) + Apple-notarized .app + .dmg	✅
Extended (long) self-test runner with live progress, result history + completion notification	✅
Pro modules (multi-machine, ML predict, cloud sync)	reserved

Known limitations

NVMeter is honest about what smartctl can and cannot do on macOS. Setting expectations up front so you don't install it and feel cheated:

✅ Fully supported

• Internal Apple SSD (NVMe via Apple Fabric) — temperature, wear, spare, media errors.
• Thunderbolt 3 / 4 / 5 NVMe enclosures and docks — read as native PCIe, no quirk needed. Full NVMe smart-log.
• USB-NVMe enclosures with cooperative bridge chips (JMicron JMS583, ASMedia ASM2362, Realtek RTL9210, etc.) — typically work via -d sat,16 or vendor-specific -d flags. See NVMeter-drivedb for verified entries.

⚠️ Often blocked: USB-SATA enclosures and external HDDs

Many USB-SATA bridge chips refuse to pass SMART commands through on macOS, returning Operation not supported by device regardless of which -d argument is tried. This is not a NVMeter bug — it's a fundamental limitation of macOS's user-space SCSI stack.

For context: Linux's kernel includes a generic SAT (SCSI/ATA Translation) layer in sd_mod that handles most USB-SATA bridges transparently. macOS has no equivalent. Closed-source tools like DriveDx work around this by shipping their own SATSMARTDriver kernel extension, but kext requirements on Apple Silicon (SIP disabled, Reduced Security boot, etc.) make this a non-starter for an open, frictionless install. NVMeter does not ship a kext.

Known macOS-blocked families include WD Elements / My Passport (1058:25a3 and relatives), most older Seagate Backup Plus, and various no-brand USB-SATA enclosures. When NVMeter detects one, it shows a friendly "SMART pass-through blocked by macOS — try an NVMe enclosure or use Linux" message instead of a scary error.

⛔ Not supported

• CD/DVD drives, MMC/SD card readers, RAID volumes. Out of scope.
• Drives behind hardware RAID controllers that hide the underlying disks.
• Disk images (disk4, disk5 style synthetic devices) — they have no underlying physical drive to query.

Building from source

Requirements: macOS 14+ (Sonoma), Xcode 15+ / Swift 5.9+, smartmontools installed (brew install smartmontools).

git clone https://github.com/hualiu77/NVMeter.git
cd NVMeter
swift build
swift test
swift run NVMeterApp        # for development; shells out to /opt/homebrew/bin/smartctl

To build a signed, notarized .app + .dmg like the one on the Releases page:

# One-time keychain setup (creates an app-specific password on appleid.apple.com first):
xcrun notarytool store-credentials nvmeter-notarize \
    --apple-id "<your-apple-id>" --team-id <your-team-id>

# Then any release build is a single command:
NOTARIZE=1 MAKE_DMG=1 bash scripts/build-app.sh

This produces build/NVMeter.app, build/NVMeter-<ver>.zip, and build/NVMeter-<ver>.dmg, all signed with your Developer ID and stapled with Apple's notarization ticket. See scripts/build-app.sh for the full pipeline.

Contributing

• Adding support for a new USB/Thunderbolt enclosure? Send a YAML PR to NVMeter-drivedb — no Swift required. See its CONTRIBUTING.md.
• Code changes? See CONTRIBUTING.md. All non-trivial PRs require a signed CLA so we can keep the open-core licensing options open without ever changing what's free.

License

NVMeter is licensed under AGPL-3.0-or-later — see LICENSE.

NVMeter embeds and depends on smartmontools (smartctl), licensed under GPL-2.0-or-later. See NOTICE for full attribution and how to obtain the corresponding source code.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. NVMeter is not a substitute for backups.