Transfer Speed

Native macOS (SwiftUI) tool for measuring file transfer speed. Requires macOS 15+.

Copy — pick or drop files/folders and a destination. Copies them while showing live MB/s, a speed graph, progress, ETA, average and peak. Never overwrites: stops if an item with the same name already exists. Preserves permissions, timestamps, extended attributes and symlinks (macOS also marks every copy with a quarantine attribute, as it does for all files sandboxed apps write).

Benchmark — pick a drive (internal, USB, Thunderbolt, mounted SMB/AFP/NFS share) or any folder. Writes a 1–10 GB test file, flushes it to the device, reads it back, deletes it, and reports sequential write/read speed.

The app is sandboxed: it only touches files and folders you pick or drop on it. The first test of an external or network drive asks, once, for permission to write to it.

How it measures

• Raw POSIX read/write in 8 MB chunks with F_NOCACHE, so the page cache in RAM doesn't inflate results.
• Benchmark write time includes F_FULLFSYNC (falls back to fsync on shares that lack it).
• Live speed is a 1-second sliding window; final numbers are total bytes ÷ total time.
• Speeds are decimal MB/s (1 MB = 1,000,000 bytes), like drive spec sheets and most disk tools.

Install

Download the .dmg from Releases, open it, and drag Transfer Speed to Applications. Universal build: runs on Apple Silicon and Intel.

The app is ad-hoc signed, not notarized, so macOS blocks the first launch. Open it once, then go to System Settings → Privacy & Security and click Open Anyway.

Build

./build.sh                    # build/Transfer Speed.app
./build.sh dmg                # also build/TransferSpeed-<version>.dmg
./build.sh mas <profile>      # Mac App Store package build/TransferSpeed-<version>.pkg

With a Developer ID Application certificate in the keychain, the app and DMG are signed with it (hardened runtime, secure timestamp); otherwise they are signed ad-hoc. To also notarize and staple the DMG, store credentials once and pass the profile name:

xcrun notarytool store-credentials TransferSpeed --apple-id <apple-id> --team-id <team-id>
NOTARY_PROFILE=TransferSpeed ./build.sh dmg

For the Mac App Store build and the remaining account-side steps, see docs/APP_STORE.md.

Other commands:

swift run          # run without bundling
swift test         # engine tests

Layout

• Sources/TransferSpeed/Engine.swift — copy planner/executor, benchmark I/O, cancellation
• Sources/TransferSpeed/Jobs.swift — observable view models and speed sampling
• Sources/TransferSpeed/*View.swift, Components.swift — UI
• scripts/make-icon.swift — renders the app icon

License

MIT — see LICENSE.