FluxDown

Downloads, Supercharged.

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


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Highlights

• Dynamic download acceleration — Rust + Tokio engine with adaptive segmentation and slow-segment rescue
• Multi-protocol — HTTP/HTTPS, FTP, BitTorrent, eD2K, HLS & DASH streaming
• One engine, multiple clients — native GPUI desktop, Kotlin Android and SwiftUI iOS apps, React Web UI and CLI
• Browser integration — Chrome / Edge / Firefox extension with a 3-layer interception engine, plus a userscript
• AI-agent ready — built-in MCP (Model Context Protocol) server: let Claude, Cursor & other AI clients manage your downloads
• Automation & remote management — RSS subscriptions, scheduled queues, webhooks, plugins and optional FluxCloud device collaboration
• Local-first — free and open source, no ads, no account required for local downloads; resumable state stored locally by default

Features

FluxDown vs. IDM

Installation

Browser Extension

NAS / Server

docker compose -f docker/docker-compose.yml up -d

• Server mode listens on 0.0.0.0:17800 by default; override it with FLUXDOWN_BIND.
• For unattended setup, supply FLUXDOWN_TOKEN through your deployment environment or secret manager, not a committed file. It initializes the key only if one has not already been set.
• Persist /data for the database, logs and access key, and /root/Downloads for downloads. The supplied Compose file uses a named data volume and docker/downloads/ on the host.
• Prefer SSD/cache storage for /data if download disks need to sleep.
• Native deployments must keep fluxdown-agent and fluxdownd in the same directory.

CLI & HTTP APIs

fluxdown ping
fluxdown add "https://example.com/file.zip"
fluxdown --json list

# Standalone mode: embed the engine instead of connecting to a service
fluxdown add --local "https://example.com/file.zip"

MCP Server (Model Context Protocol)

• Endpoint: http://127.0.0.1:17800/mcp for the default desktop configuration; use your server address for headless deployments
• 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 (12)

Client configuration

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

Architecture

flowchart TD
    UI["GPUI desktop"] -->|"WebSocket /rpc"| AGENT["fluxdown-agent — UI gateway and desktop shell"]
    WEB["React Web UI"] -->|"WebSocket /rpc"| AGENT
    EXT["Browser Extension (WXT)"] -->|Native Messaging| NMH["fluxdown_nmh"]
    NMH --> AGENT
    CLI["fluxdown CLI"] -->|"HTTP API"| AGENT
    AGENT -->|"Authenticated JSON-RPC"| DAEMON["fluxdownd — download core"]
    DAEMON --> ENGINE["fluxdown_engine"]
    MOBILE["Native Android / iOS"] -->|"UniFFI"| CORE["fluxdown_mobile"]
    CORE -->|"embedded or remote"| AGENT
    LOCAL["fluxdown add --local"] --> ENGINE
    ENGINE --> PROTOCOLS["HTTP/HTTPS, FTP, BitTorrent, eD2K, HLS, DASH"]
    ENGINE --> DB[("SQLite / PostgreSQL")]

• Daemon owns downloads: engine, download database, queues, RSS, plugins and webhooks.
• Agent owns integration: UI gateway, FluxCloud account/sync, device collaboration, browser capture and desktop tray/lifecycle.
• Shared contracts: native/protocol defines transport-independent DTOs, methods and events; native/api exposes REST, aria2 and MCP through ApiHost, without depending on the engine.
• Engine independence: EventSink and HostSelection connect the engine to hosts. Only one engine may write to a data directory at a time; the diagram shows alternative hosts, not concurrent writers.

Building from Source

# Clone the development branch (main = active development, stable = stable releases)
git clone -b main https://github.com/zerx-lab/FluxDown.git
cd FluxDown

Desktop (GPUI)

# Build desktop UI, agent, daemon and browser relay, then launch
cargo desktop-dev

# Build only (also stages a signed development .app on macOS)
cargo desktop-dev --build-only

Headless server & Web UI

# Build the Web UI BEFORE building the agent
cd web
bun install --frozen-lockfile
bun run build
cd ..

cargo build -p fluxdown_daemon
cargo run -p fluxdown_agent --features web-ui -- --server

CLI

cargo build -p fluxdown_cli
cargo run -p fluxdown_cli -- ping

Native mobile

# Android: use Android Studio's JBR as JAVA_HOME
(cd mobile/Android && ./gradlew :core:testDebugUnitTest :bridge:testDebugUnitTest :app:assembleDebug)
# iOS: from repository root
mobile/FluxDown/scripts/build-core.sh
(cd mobile/FluxDown && xcodebuild build -project FluxDown.xcodeproj -scheme FluxDown -destination 'generic/platform=iOS Simulator')

cargo test -p fluxdown_engine        # Engine tests
cargo test -p fluxdown_api           # HTTP / aria2 / MCP contracts
cargo test -p fluxdown_agent         # Gateway / server
cargo test -p fluxdown_cli           # CLI
cd web && bun test && cd ..          # Web UI
cargo test -p fluxdown_mobile        # Shared native mobile core

Contributing & Community

• Bug reports / feature requests — GitHub Issues or the website feedback page
• QQ Group — 832143651

cargo fmt --check
cargo clippy --workspace --all-targets -- -D warnings

License