A macOS menu-bar app (and CLI) that surfaces the full truth about an SD card inserted into your Mac: its real identity, whether it looks genuine, and (with Pro) its real usable capacity.
Status: early development. The read layer works: WhatSDCore +
WhatSDDarwinBackend and the whatsd CLI read the built-in SD slot (identity,
negotiated link, volumes) and flag likely counterfeits. The menu-bar app shows
the same, styled.
SD cards are opaque and their printed badges (Class 10, U3, V30, A2) are poorly understood and frequently faked. WhatSD answers two questions the Mac doesn't answer cleanly:
- Is this card real? Counterfeit SD cards are everywhere. WhatSD flags suspect cards from their identity registers, and the Pro capacity test proves the real usable size by writing and verifying data across the card.
- Is it as fast as the box claims? macOS can't read the speed-class registers, so the only honest answer is a real measured benchmark.
On the built-in SD slot, system_profiler and IOKit expose the card's identity
(manufacturer, product, serial, manufacture date, spec version, capacity,
format) and the negotiated electrical link, with no special entitlements. macOS
does not expose UHS / Video / App speed classes, so real speed must be measured.
USB card readers hide the card's identity behind a generic bridge; WhatSD says
so rather than guessing.
WhatSDCore— pure models, formatting, counterfeit heuristics, and the capacity-test engine. No OS imports.WhatSDDarwinBackend— IOKit / DiskArbitration /system_profilerreaders.WhatSDAppKit— shared UI plumbing (the Pro extension registry, font scaling).WhatSDApp— the SwiftUI menu-bar app.whatsd-cli— thewhatsdcommand-line tool.
swift build
swift test
scripts/smoke-test.sh # build + bundle WhatSD.app + smoke-test
The app and its read layer are MIT licensed (see LICENSE). The Pro capacity
test is a separate paid feature and is not open source.