Throttle

A free, open-source NetLimiter-style bandwidth monitor and limiter for Windows, written in Rust. It shows live per-process download/upload rates and lets you cap or block any process's network traffic, with no license nags and no telemetry.

What it is

Throttle watches every network flow on your machine, attributes it to the owning process, and optionally shapes it:

• Live monitoring: per-process download and upload rates, totals, and active flow counts, refreshed about once a second.
• Per-process limits: cap a process's download and/or upload speed (for example, hold a game updater to 2 MB/s).
• Blocking: drop all traffic for a process entirely.
• Persistent rules: rules are matched by executable path, so they survive restarts and re-apply automatically when the process launches again.

Traffic interception uses WinDivert, a signed, well-established user-mode packet-diversion driver, so Throttle does not need its own kernel driver.

Throttle-demo.mp4

Features

• Native GUI (egui/eframe): sortable process table, total-traffic graph, and a per-process history sparkline.
• Humanized rates and totals (B/s, KB/s, MB/s, GB/s, base 1024).
• Right-click any process to set a download limit, set an upload limit, block, unblock, or remove its rule.
• Rate editor uses a number field plus a unit dropdown (B/s, KB/s, MB/s, GB/s).
• System tray icon, with optional minimise to tray, close to tray, start minimised, and launch at Windows startup (Settings menu). Startup uses a Task Scheduler logon task, since Windows skips Run-key entries that need elevation.
• Optional colour themes (Themes menu): editor and community palettes, import of any editor colour theme JSON, Customise (corners, density, scale, fonts, accents) and View (columns, plot, always on top, compact). Stock by default.
• Filter box above the table (Ctrl+F) and an Active chip that hides idle processes. The window size and position, panel sizes, column widths and sort order are remembered across restarts.
• Plot navigation: scroll zooms the time axis, drag pans it, double click resets the view.
• Rules can be switched off and back on without losing them, from the right-click menu or the tray menu, which lists every rule with a check mark. The tray tooltip shows the live download and upload totals.
• Runs as a single elevated process; engine and GUI communicate over channels.

Download

Prebuilt Windows binaries are available on the Releases page. Grab the latest Throttle-vX.Y.Z-windows-x64.zip, extract it anywhere, and run throttle.exe. The WinDivert driver files are included in the zip, so no extra setup is needed. Windows will show a UAC prompt because the app needs administrator rights (see below).

Screenshots

Live rates per process, with the selected process on the right and a button that opens its folder:

The Themes menu, with editor and community palettes:

Customise: corners, density, scale, fonts and accents:

The filter box and the Active chip narrow the table to what matters:

Building

You need a recent stable Rust toolchain (2024 edition) and the WinDivert files vendored in this repo under vendor/WinDivert-2.2.2-A/x64.

# From the repository root:
cargo build --release

The build links against WinDivert using the import library at vendor/WinDivert-2.2.2-A/x64 (wired up via WINDIVERT_PATH in .cargo/config.toml), and embeds a requireAdministrator manifest through the embed-manifest build script.

Running

WinDivert is loaded dynamically at runtime. Copy its two runtime files next to the built executable before running:

copy vendor\WinDivert-2.2.2-A\x64\WinDivert.dll   target\release\
copy vendor\WinDivert-2.2.2-A\x64\WinDivert64.sys target\release\

Then launch it:

target\release\throttle.exe

Administrator requirement

Throttle must run as Administrator, because WinDivert can only open its device from an elevated process. The embedded manifest requests elevation, so Windows shows a UAC prompt on launch. If the backend can't start (not elevated, or the WinDivert files are missing), the app opens a small window explaining the error instead of exiting silently.

Antivirus note

WinDivert is a legitimate packet-capture driver, but because it is also used by some game "boosters" and, occasionally, by malware, a few antivirus products flag it heuristically. The files vendored here come from the official signed WinDivert 2.2.2 release. If your AV quarantines WinDivert64.sys or WinDivert.dll, verify them against the official distribution at https://reqrypt.org/windivert.html and allow-list them if you trust the source.

VPNs and web-filtering proxies

Some security products (for example NordVPN Threat Protection) intercept browser connections and route them through a local proxy on the same machine. While such a feature is active, the proxy process is the one talking to the internet, so Throttle shows the browser's traffic under the proxy's process (such as nordsec-threatprotection-service) and a limit set on the browser itself has no effect; set it on the proxy process instead. Throttle does not capture loopback traffic, so the interception itself keeps working.

Support

Throttle is free, with no ads and no telemetry, and is built in my spare time. If it saved you some frustration, you can buy me a coffee. Stars, bug reports and pull requests are just as welcome.

License

• Throttle's own source code is licensed under the MIT License (see LICENSE).
• WinDivert (WinDivert.dll, WinDivert64.sys, headers/import lib) is a separate project licensed under the LGPL v3 (with a GPL/proprietary dual option). Throttle links to it dynamically and ships it as a separate, replaceable DLL/driver; it is not statically linked into the binary. See vendor/WinDivert-2.2.2-A/LICENSE for the full text and terms.

The MIT code and the LGPL WinDivert component stay independently licensed. Replacing the bundled WinDivert files with your own build is supported.