DiskSpeed is a fast, no-nonsense disk benchmark for macOS - measure the real read and write speeds of any internal SSD or external USB drive in seconds.
Pick a drive from the sidebar, choose a test size, and hit Run. DiskSpeed writes and reads real data, shows live throughput as it goes, and keeps a history so you can compare drives at a glance.
Highlights
- Sequential read & write - large-block throughput in MB/s, the number that matters for big file transfers and video.
- Random 4K IOPS - random read and write operations per second, the real measure of everyday app and system responsiveness.
- Every drive, one place - internal SSDs and external USB drives auto-detected in the sidebar with capacity and filesystem.
- Live progress - watch throughput update in real time through each phase of the test, no guessing when it's done.
- Choose your test size - 256 MB for a quick check, 1 GB or 4 GB for results that survive drive caching.
- Detailed result charts - click any result to break sequential and random performance out into clear read-vs-write panels.
- Run history - past benchmarks are saved so you can compare drives or track a disk over time.
- Native & light - a tiny native macOS app with light, dark, and auto themes that respects your system appearance.
How it works
DiskSpeed runs an actual read/write workload against the drive you select - it doesn't estimate from specs. Sequential passes move large blocks to gauge raw bandwidth, while the random 4K pass fires many small operations to measure IOPS. A bigger test size reduces the effect of on-drive caching, so choose 1 GB or 4 GB when you want the most honest numbers.
Perfect for
- Buying a drive - confirm a new SSD or USB stick actually hits its advertised speed.
- Creators & editors - check that your scratch disk keeps up with 4K and ProRes workflows.
- Spotting a slow disk - catch a failing or throttled drive before it costs you a deadline.
- Comparing drives - benchmark several drives and let the saved history settle the argument.
