How to Test an SD Card on Mac, Windows and Linux

Important Things Before Testing

Backup Your Data: Testing usually involves formatting, which erases everything on the SD card.

Expected vs. Advertised Speed: SD cards have varying speeds. Be realistic and compare tested speeds against their rated speeds advertised by the manufacturer.


1. H2testw (Comprehensive Health Check)

  • Download H2testw: It’s free from []. Click the download link for your language.
  • Insert the SD card and run H2testw.
  • Choose the target drive (your SD card).
  • Click “Write + Verify”. This fills the card with data and then verifies it, checking for errors.

2. CrystalDiskMark (Performance Testing):

  • Download CrystalDiskMark: []
  • Install and run CrystalDiskMark.
  • Select your SD card and run the benchmark with default settings.
  • You’ll get read/write speeds.


1. Disk Utility (Built in, Light Testing):

  • Open Disk Utility (Applications –> Utilities).
  • Select your SD Card.
  • Click “First Aid” and then “Run”. This will check for file system errors.

2. Blackmagic Disk Speed Test (Performance Focus):

  • Download from the Mac App Store
  • Run the app and select your SD Card.
  • Click “Start” to run a speed test.


1. F3 (Command Line, Health Check):

  • Install F3: Use your package manager (sudo apt install f3 on Debian/Ubuntu).
  • Check your SD Card device path with lsblk.
  • Run f3write /path/to/your/SDcard (replace with the correct path) to fill the card and test for errors.
  • Run f3read /path/to/your/SDcard to verify the written data.

2. dd (Command Line, Detailed Control):

You can use the dd command with various options to test read/write speeds and stress test your card. Be careful! Use with caution or don’t use at all if you don’t know what you’re doing.

Other Things

Manufacturer Tools: Some SD card manufacturers offer their own diagnostic utilities. Check their websites.

Interpretation: Pay attention to error messages, slow speeds, or huge discrepancies between advertised and actual performance, which could indicate a failing SD card.

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