Push your Mac to the redline.
A native macOS app that drives your CPU, GPU, memory and disk to their limits — with a live system monitor — all in one window that looks like part of macOS.
Sometimes you need to know how your Mac behaves under load — checking thermals, validating a fresh machine, burning in new hardware, or just seeing how far it goes. Most stress tools are either command-line gymnastics or cross-platform apps that feel foreign on a Mac.
Redline is the alternative: one native SwiftUI window that saturates every subsystem on demand and shows you exactly what's happening, in real time.
- 🧮 CPU — multi-core load across every logical core, with Float / Integer / Mixed workloads and an optional auto-stop timer
- 🎮 GPU (Metal) — a heavy compute kernel saturates the GPU; configurable buffer size, live iterations/sec
- 🧠 Memory — allocates and continuously touches a chosen amount of RAM
- 💽 Disk I/O — sequential / random read & write throughput (cache-bypassing)
- 📊 Live system monitor — overall CPU / memory / swap plus a per-core grid, sampled natively via Mach/sysctl, with a timestamped activity log
- 🎨 Looks like a Mac app should — SF Symbols, vibrancy, native controls, and a single Start/Stop toggle per test
- Grab the latest Redline-x.y.z.zip from Releases.
- Unzip and drag
Redline.appinto/Applications. - The build is unsigned, so on first launch right-click the app → Open, then confirm once to let Gatekeeper through.
git clone https://github.com/marco-scheffler/redline.git
cd redline
open Redline.xcodeproj # then press Run (⌘R)The Xcode project is committed, so it opens and runs without any extra tooling.
It is generated from project.yml with
XcodeGen; regenerate it only if you change
the project layout (xcodegen generate).
- Pick the resource you want to hammer (CPU, GPU, Memory, Disk) and tune its options.
- Press Start on that card — the icon lights up and the live monitor reacts.
- Press it again to Stop, or use Run All Tests / Stop All at the bottom.
Watch the per-core grid and the CPU / memory / swap gauges to see the impact as it happens.
- macOS 14 (Sonoma) or later (deployment minimum)
- Apple Silicon
- Xcode 26+ to build from source, with the Metal Toolchain component installed (download it separately in Xcode → Settings → Components if needed)
macOS 27 / Xcode 27: builds cleanly with Xcode 27 and runs on macOS 27, including the v1.0.0 and v1.1.0 releases. Running an Xcode 27 build on macOS 14 is not yet verified. See the compatibility review for details.
Run the tests with ⌘U in Xcode, or from the command line:
xcodebuild test -project Redline.xcodeproj -scheme Redline \
-destination 'platform=macOS,arch=arm64'This runs two suites:
- RedlineTests exercises the stress engines and the monitor on the real hardware (about 15 seconds).
- RedlineUITests clicks through the window and takes over the mouse and keyboard
for about a minute. To skip it, add
-only-testing:RedlineTests.
CI builds and runs both suites on every push to main and on every pull request.
To publish a release, push a version tag:
git tag -a v1.2.0 -m "Redline 1.2.0"
git push origin v1.2.0The release workflow runs the tests, builds the app with the version taken from the
tag, and publishes Redline-1.2.0.zip as a GitHub release.
Redline deliberately drives your hardware hard, which raises temperatures and fan speed. Keep an eye on thermals and use Stop All (or quit) to end every running test and release allocated memory.
MIT © 2026 marco-scheffler
Built with SwiftUI, Metal and Mach — no third-party dependencies.