FluxDown

Downloads, Supercharged.

A blazing fast, multi-protocol download manager — the free & open-source IDM alternative.

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Highlights

• Up to 10x faster — Rust + Tokio engine with IDM-style dynamic segmentation
• Multi-protocol — HTTP/HTTPS, FTP, BitTorrent, eD2K, HLS & DASH streaming
• Browser integration — Chrome / Edge / Firefox extension with a 3-layer interception engine
• AI-agent ready — built-in MCP (Model Context Protocol) server: let Claude, Cursor & other AI clients manage your downloads
• Resume anywhere — full download state persisted in SQLite; survive crashes and reboots
• Beautiful UI — light/dark themes, 13 color schemes, responsive three-pane layout
• Clean & private — free and open source, no ads, no tracking, no account required, local-first

Features

FluxDown vs. IDM

Installation

Grab the latest build from GitHub Releases or fluxdown.zerx.dev:

Browser Extension

Install the extension so FluxDown takes over browser downloads automatically:

MCP Server (Model Context Protocol)

FluxDown ships a built-in MCP server so AI agents (Claude Desktop, Cursor, Cline, …) can manage downloads via the Model Context Protocol. It speaks Streamable HTTP (JSON-RPC 2.0 over a single POST /mcp) on the local API port — no extra process needed.

• Endpoint: http://127.0.0.1:17800/mcp (local-only by default)
• Auth: Bearer token (Authorization: Bearer <token> or X-FluxDown-Token), shared with the management API
• Enable: Settings → API Service → toggle MCP endpoint (a token is generated automatically); the headless server enables it by default

Tools (9)

Client configuration

{
  "mcpServers": {
    "fluxdown": {
      "url": "http://127.0.0.1:17800/mcp",
      "headers": { "Authorization": "Bearer <your-token>" }
    }
  }
}

The MCP layer is implemented in native/api/src/mcp.rs on top of the same ApiHost trait that powers the REST management API and aria2-compatible JSON-RPC.

Architecture

Flutter renders the UI; a zero-FFI Rust engine does the heavy lifting. The two talk through Rinf signals, and the browser extension connects via Native Messaging.

flowchart TD
    EXT["Browser Extension (WXT)"] -->|Native Messaging| NMH["fluxdown_nmh"]
    NMH -->|Named Pipe / Unix socket| HUB
    UI["Flutter UI (shadcn_ui)"] <-->|Rinf signals| HUB["hub — FFI adapter"]
    HUB --> ENGINE["fluxdown_engine"]
    ENGINE --> HTTP["HTTP/HTTPS"]
    ENGINE --> FTP["FTP"]
    ENGINE --> BT["BitTorrent"]
    ENGINE --> ED2K["eD2K"]
    ENGINE --> HLS["HLS / DASH"]
    ENGINE --> DB[("SQLite")]

Building from Source

Prerequisites: Flutter SDK · Rust toolchain · Rinf CLI

# Check your environment
rustc --version
flutter doctor

# Install the Rinf CLI (once)
cargo install rinf_cli

# Fetch dependencies & generate Dart bindings
flutter pub get
rinf gen

# Run in debug mode
flutter run

# Build a release
flutter build windows --release   # or: macos / linux

# Debian/Ubuntu
sudo apt-get install cmake ninja-build clang pkg-config \
  libgtk-3-dev libayatana-appindicator3-dev libnotify-dev libsecret-1-dev patchelf zstd

# Arch Linux
sudo pacman -S cmake ninja clang pkgconf gtk3 libayatana-appindicator libnotify libsecret patchelf zstd

flutter test                          # Dart tests
cargo test -p fluxdown_engine        # Rust engine tests
cargo test -p hub                    # FFI adapter tests

Contributing & Community

• Bug reports / feature requests — GitHub Issues or the in-app feedback dialog
• QQ Group — 832143651

Pull requests are welcome! Before submitting, please make sure:

cargo fmt --check && cargo clippy -- -D warnings   # Rust
flutter analyze                                     # Dart

License

Distributed under the GNU Affero General Public License v3.0.