PerfWindowCPU
Load per core, package and core temperatures, clocks, Vcore, RAPL power and headroom to TjMax. Intel P-cores and E-cores are shown apart.
- Hardware
- Every major component
- Refresh
- Every 0.5, 1, 2 or 5 s
- When closed
- Nothing left running
- Telemetry
- None
What it monitors
Built on LibreHardwareMonitor, the open-source sensor library behind many Windows monitoring tools. Every row has a tooltip that explains it in one plain sentence.
GPU
Discrete NVIDIA and AMD cards and Intel integrated graphics: load, core, hot spot and memory junction temperatures, clocks, encoder load, fan, power and VRAM.
Memory
Used, cached and pagefile, plus per-module DIMM temperatures where the modules report them, with vendor, part number and timings on hover.
Storage
Temperature against each drive's own limits, activity, capacity and health, and SMART lifetime on hover: power-on hours, NVMe wear and data written.
Board, fans and power
Motherboard and VRM temperatures, fan speeds and voltage rails, battery charge rate and health, and the board model and BIOS version.
Network and themes
Throughput and link use, with SSID and signal on Wi-Fi. Six themes, from CRT amber to a plain light one, can follow Windows' light and dark setting.
The window
Cards scale to fill any window, from 720×500 up to a 4K screen, with no scroll bar; the least important readings step aside first. Backgrounds can be made see-through from 100 % down to 30 %, and the window collapses into a one-line strip of live values that sits over the top of the screen without taking any of it.
The terminal
perfwindow-cli opens the same readings as a live dashboard in your terminal, in your theme, with load and temperature history. Scripts and AI agents get a plain report, one reading per line, or JSON with --json.
In the terminal
New in 2.1: perfwindow-cli brings every reading to the command line, for when you'd rather not open a window, and for scripts and AI agents that read text. Turn it on in Settings → Command line, which also adds it to your PATH.
A dashboard in your terminal
The window's cards in your theme, with load and temperature history, fitted to the terminal's size. It runs in Windows Terminal and in the classic console, and q leaves it.
For scripts
Piped or redirected, it prints one plain report instead, one Label: value reading per line. --once prints a report and exits; --watch 5 prints one every 5 seconds.
For AI agents
perfwindow-cli --json gives an agent the machine's loads, temperatures, clocks, power and drive health as JSON, so it can check why a build is slow or a laptop runs hot without a screenshot.
How it works
Two programs, one installer: a dashboard that runs as you, and a sensor service that runs only while the dashboard is open.
A dashboard that runs as you
PerfWindow.exe is a Rust and egui app without administrator rights. It draws the cards and talks to the sensor service over a named pipe.
A sensor service on demand
Reading CPU registers and drive SMART data needs administrator rights, so a .NET service built on LibreHardwareMonitor does it. Windows asks once per launch to start it.
First readings in about a second
The service opens the CPU and memory sensors first, then the board, GPU, drives, network and battery, while the loading screen shows its progress.
Gone when you close it
The service exits as soon as the dashboard disconnects. No tray icon, nothing at startup, and the uninstaller removes every file and your settings.
Tested, and honest about limits
How it's verified
- 416 Rust tests for the dashboard and 112 .NET tests for the sensor service run on every push to main and every pull request.
- Clippy with warnings as errors, format checks and a
cargo auditof every Rust dependency. - CI then builds the full installer, with the license texts of every bundled component.
What it can't do
- Read what the hardware hides. What appears depends on the board, chips and drivers, and some machines report only part of it.
- Change anything. It reads sensors only: no overclocking, undervolting or fan control.
- Skip the prompt. Admin-only sensors need one approval per launch. The installer isn't code-signed yet, so SmartScreen warns.
- Move the strip by itself. The mini strip stays on the monitor it was last on and covers its top edge; if that monitor goes away it moves to the one the window is on.
Questions
Is PerfWindow free?
Yes. PerfWindow is free and open source under the MIT License. It has no ads, accounts or telemetry.
Does PerfWindow keep running in the background?
No. The sensor service starts when you open PerfWindow and exits when you close it. There is no tray icon and nothing starts with Windows.
Why does PerfWindow ask for administrator approval when it starts?
CPU temperatures, clocks and power, and drive SMART data, can only be read with administrator rights. PerfWindow runs the dashboard as you and asks Windows once per launch to start its sensor service, which reads the hardware.
Can PerfWindow change my hardware settings?
No. PerfWindow only reads sensors. It doesn't overclock, undervolt, change fan curves or write to any hardware setting.
What is PawnIO and why does the installer add it?
PawnIO is a small, signed kernel driver that LibreHardwareMonitor uses to read CPU temperature, clock and power registers. The installer adds it unless a current version is already installed. Without it, everything except those CPU readings still works.
Does PerfWindow collect any data?
No. Its only connection is an anonymous update check against GitHub's public Releases API, at most once every six hours, which you can turn off in Settings. See the privacy statement.
Can PerfWindow stay out of the way?
Yes. The cards fill any window size, and in Settings you can make the window's backgrounds see-through from 100 % to 30 %. Press Ctrl+M, or click MINI in the title bar, to collapse the window into a one-line strip of live values over the top of the screen. It takes no screen space, doesn't take focus from the game or app you're in, and has its own opacity slider; the expand button brings the full window back.
Can a script or an AI agent read PerfWindow?
Yes. Turn on Settings → Command line, then run perfwindow-cli --json for JSON, or perfwindow-cli --once for a plain text report with one reading per line. Windows asks for the same approval as for the window, and the command and the window can't read the sensors at the same time.