fastrs

Pure-Rust speed test against Netflix's fast.com.

A single static binary that talks to fast.com's HTTP API directly. Inspired by fastcom-speed-cli and fast-cli.

Install

From source

cargo install --path .

Pre-built binaries

Grab the latest release for your platform from the Releases page.

Usage

fastrs                   # human-friendly multi-line summary
fastrs --single-line     # one-line summary
fastrs --no-upload       # skip the upload phase
fastrs --json            # machine-readable output

Example

$ fastrs
Connecting to fast.com...
Download:         2879.3 Mbps
Upload:           3102.1 Mbps
Latency unloaded:     81 ms
Latency loaded:      435 ms
Client:          203.0.113.7 / Telus
Server:          Vancouver, CA

The gap between unloaded and loaded latency is bufferbloat — how much the connection's queuing delay rises under load.

JSON output

$ fastrs --json
{
  "download_mbps": 487.2,
  "upload_mbps": 56.4,
  "unloaded_latency_ms": 11,
  "loaded_latency_ms": 38,
  "server_locations": ["Dublin, Ireland"],
  "client_ip": "203.0.113.7",
  "client_isp": "TestNet"
}

Interactive TUI

fastrs --tui

A live throughput chart, latency sparkline, and stats panel. Press q or Esc to quit.

To compile a slim binary without the TUI:

cargo install --no-default-features --path .

How it works

1. Scrape the API token from fast.com's JS bundle.
2. Hit https://api.fast.com/netflix/speedtest/v2 for a list of Netflix CDN target URLs.
3. Probe unloaded latency with sequential GETs against the first target.
4. Open 8 concurrent streamed GETs across the targets, sample bytes every 200 ms, stop when throughput stabilizes or 15 s elapses.
5. Re-probe latency mid-download to compute loaded latency / bufferbloat.
6. Repeat with concurrent POSTs for the upload phase.

Building

From the host:

minimal run build

The release binary lands at target/release/fastrs. Or run directly:

minimal run run

Development

This project is set up to build and run inside the Minimal sandbox — the toolchain (rust, gcc, binutils, …) is pinned in minimal.toml, so no host install is required beyond the minimal CLI.

CLI naming: on the host the binary is minimal. Once you're inside a sandbox (e.g. via minimal run dev) the same tool is exposed as min. The examples below use whichever name matches the context.

Tasks are defined in minimal.toml. From the host:

minimal run dev          # interactive zellij dev session (Claude pane + shell pane)
minimal run build        # cargo build --release
minimal run run          # cargo run --release
minimal run fast-rs-debug # cargo run --release with RUST_LOG=debug
minimal run test         # unit tests
minimal run test-live    # also run the live integration test against fast.com
minimal run lint         # cargo clippy --all-targets -- -D warnings
minimal run fmt          # cargo fmt

From inside the sandbox shell :

min run build        # cargo build --release
min run run          # cargo run --release
min run fast-rs-debug # cargo run --release with RUST_LOG=debug
min run test         # unit tests
min run test-live    # also run the live integration test against fast.com
min run lint         # cargo clippy --all-targets -- -D warnings
min run fmt          # cargo fmt

minimal run dev

Launches a zellij layout (zellij.kdl) via scripts/setup-dev.sh with two panes:

• left — Claude Code (claude --dangerously-skip-permissions, only safe because the sandbox is ephemeral).
• right — a bash shell that first runs scripts/dev-shell.sh (a quick cheat sheet of available min run <task> shortcuts) and then drops you into an interactive prompt.

The session is named dev and is reset on each invocation.

Without Minimal

The equivalent cargo commands (cargo build --release, cargo test, cargo clippy --all-targets -- -D warnings, cargo fmt) work too.

CI runs cargo test --lib, cargo fmt --check, and cargo clippy --all-targets -- -D warnings on Linux/macOS/Windows. Tagged pushes (v*) build cross-platform release archives via .github/workflows/release.yml.

Layout

• src/api.rs — fast.com token discovery + targets API
• src/measure/ — orchestrator and per-phase code (latency / download / upload)
• src/output.rs — JSON, single-line, and multi-line summary renderers
• src/tui.rs — live TUI (gated on the tui feature, default on)
• tests/end_to_end.rs — #[ignore]'d live integration test
• docs/plans/ — design and implementation plans for past features

Cargo features

• tui (default) — pulls in ratatui + crossterm, enables --tui. Disable with --no-default-features for a smaller binary.

License

Apache-2.0. See LICENSE.