Diskio: Disk & SSD Speed Test

How fast is your storage? Measure sequential read and write speeds on your iPhone or a compatible external drive. Go beyond one number with repeat runs and a detailed report.

SEE THE WHOLE RESULT
Choose 1, 3 or 6 runs. With 3 or 6 runs, see median read and write speeds, minimum and maximum values, and the result of every run.

CHECK CONSISTENCY
Choose 6 runs to assess read and write stability separately over the last five. See whether results are stable or vary, with the criteria explained in the app.

TEST YOUR SETUP
Use your iPhone's internal storage or select a compatible, writable external drive through Files. Choose a test file from 1 to 5 GiB and a block size of 1, 2, 4, 8 or 16 MiB. The defaults are 6 runs, a 1 GiB file and a 2 MiB block.

UNDERSTAND THE MEASUREMENT
Speeds are shown in MB/s, and write timing includes final filesystem synchronization. Follow each write and read phase as the test runs.

SHARE THE DETAILS
Send a result card with the full report, test settings and, after 6 runs, the stability assessment. The interface supports light and dark appearances, larger text and Reduce Motion.

ADAPTS TO YOUR DISPLAY
On iPhone Duo, an expanded layout gives controls and results their own space. Your report stays available as the layout changes, and narrow windows use a compact view.

GET STARTED
1. Select your storage and test settings.
2. Start the test and keep Diskio open.
3. Review the report or share your results.

A test needs enough free space for a temporary file. External storage must be accessible and writable through Files. Results depend on the device, storage, connection, free space and test settings.

The stability assessment adapts numerical criteria from SNIA SSS PTS. It is not a full SNIA-compliant benchmark, a drive-health check or a sustained-performance rating. Results from version 3.0 onward may differ from older versions because the measurement method was revised.