flux.

Your media. Your space.

A fast, private, self-hostable media workspace. Paste a link, pick a format, save it offline. Built with plain HTML, CSS and ES modules on the front end, and Node.js and FFmpeg on the back end. No frontend build step. Two runtime dependencies.

Just want to use it? Download the desktop app for Windows, macOS (Apple Silicon) or Linux from the latest release. No setup needed.

Want to contribute? Pick a good first issue, say hi in Discussions, and open a PR. Setup takes about a minute: npm ci && npm run setup && npm run dev.

Features · Screenshots · Desktop app · Quick start · Configuration · Architecture · Security · Deploy · Contributing

_{47-second product demo. Watch the full-quality MP4.}

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✨ Features

Download workflow

• Three ways to find media: paste a single link, paste a batch of links, or search by keyword.
• Metadata first, download second. Flux resolves the real title, creator, duration and available resolutions before you commit to anything.
• Video (MP4) or audio (MP3), with a resolution cap (only resolutions the source really offers, no fake upscaling) and MP3 bitrates of 128/192/256/320 kbps.
• Subtitle embedding and language selection where the source provides them.
• Playlists become individual jobs, each validated separately.
• Live queue with real progress. When total bytes are unknown the progress is null. Flux never invents a percentage.
• Cancel, retry, regenerate and clear actions, all scoped to the owner.
• Resumable downloads through HTTP range requests on the file endpoint.
• Automatic cleanup: finished files expire after a configurable retention window (24 h by default), while history records stay and offer one-click regeneration.

Guests vs. signed-in users

	Guest	Signed in with Google
Inspect and search links	✅	✅
Download genuine 50% previews	✅	✅
Full-length downloads	❌ (401 at the API)	✅
Private download library	per-browser	per account
Guest records carry over on sign-in	n/a	✅

Genuine previews, not trimmed fakes

Guest previews are produced by FFmpeg on the server. Flux probes the real duration of the downloaded source, re-encodes from the beginning to exactly half of the measured runtime, runs FFprobe on the output, and fully decodes it to catch corruption. Only a validated file is ever offered for download, and the full-length source is deleted straight after.

Source-aware interface

Paste a link and the whole workspace re-themes to match the platform (surface, type, controls and colour tokens) with a single bottom-up colour sweep. TikTok and X get a dark treatment, the rest get distinct light ones. Mixed batches and unknown URLs keep the Flux default, and the sweep is disabled for users who prefer reduced motion.

15 supported source families

YouTube · TikTok · Instagram · X / Twitter · SoundCloud · Pinterest · Vimeo · Dailymotion · Twitch · RadioJavan · Reddit · Facebook · Bilibili · Archive.org · Wikimedia

These are conditional source families powered by the media engine's extractors, not individually guaranteed integrations. Platforms change often. Operators can add reviewed hosts with FLUX_EXTRA_SOURCE_HOSTS.

Craft and accessibility

• Semantic HTML, responsive from 1440 px down to 320 px, an auto-collapsing desktop rail and a mobile drawer.
• Keyboard-first: skip link, a / quick-access shortcut, managed dialog focus and full tab order.
• Automated axe-core WCAG A/AA checks on every page and the auth dialog at 1440, 390 and 320 px.
• Respects prefers-reduced-motion.

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📸 Screenshots

Lookup → choose. Real metadata, detected resolutions, MP4/MP3.	Source-aware theming. Paste a TikTok link and the workspace goes dark.
My downloads. Live progress, queue state and one-click saves.	History. Expired files keep their record and can be regenerated.
Google sign-in. Server-side OAuth with PKCE, identity only.	Mobile. Fully responsive down to 320 px.

_{Screenshots are generated from fixture data with node scripts/screenshots.mjs, so they never show real user content.}

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🖥 Desktop app

Don't want to run a server? Flux also ships as a desktop app:

System	Download
Windows	Flux-Setup-*.exe
macOS (Apple Silicon)	Flux-*.dmg
Linux	Flux-*.AppImage

Get them from the latest release, open the app, paste a link and save. Full-length downloads work without Google sign-in, and the first launch needs an internet connection to fetch its media engine.

The builds are unsigned, so Windows SmartScreen (More info, then Run anyway) and macOS Gatekeeper (right-click the app, then Open) show a warning the first time. Developer notes are in desktop/.

Desktop app troubleshooting

• Windows says "Windows protected your PC": click More info, then Run anyway.
• macOS says the app can't be opened: right-click (or Control-click) the app, choose Open, then confirm. If it still refuses, go to System Settings, Privacy & Security and click Open Anyway.
• The macOS download only supports Apple Silicon (M1 or newer). Intel Macs can run Flux from source (see Quick start).
• Linux: make the AppImage executable first: chmod +x Flux-*.AppImage.
• "Flux could not start": the first launch needs internet to fetch its media engine. Connect and try again.
• Downloads that used to work now fail: sites change often. The app updates its media engine each time it starts, so restart it. If it still fails, open an issue and pick Desktop app problem.
• Where your data lives: Windows %APPDATA%Flux, macOS ~/Library/Application Support/Flux, Linux ~/.config/Flux. Deleting that folder resets the app.

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🚀 Quick start

Requirements: Node.js 22.9+ (24 LTS recommended). npm run setup downloads the media engine for you (checksum-verified) and, on Windows x64, FFmpeg/FFprobe too. On macOS/Linux install FFmpeg with your package manager (brew install ffmpeg, apt install ffmpeg).

git clone https://github.com/10k11/flux.git
cd flux
npm ci
npm run setup     # fetches the media engine (and FFmpeg on Windows) into ./bin
npm start

Open http://localhost:3000. Guest previews work immediately, with no Google credentials needed.

cp .env.example .env   # optional: tune limits, enable Google sign-in
npm run dev            # auto-restarting dev server

Docker (with automatic HTTPS)

cp .env.example .env   # set FLUX_PUBLIC_HOST=your.domain
docker compose up -d --build

This starts Flux, an internal PO-token provider for YouTube, and Caddy, which terminates TLS and obtains certificates automatically. See Deployment.

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⚙️ Configuration

All configuration is through environment variables (loaded from .env by npm start).

Variable	Default	Purpose
FLUX_ORIGIN	http://localhost:3000	Canonical public origin. HTTPS required outside localhost. No trailing slash.
GOOGLE_CLIENT_ID / GOOGLE_CLIENT_SECRET	none	Enables Google sign-in. Server-side only.
FLUX_PUBLIC_HOST	none	Domain used by Docker Compose and Caddy.
FLUX_PUBLIC_OPEN	0	1 = open to the internet (rate limits apply).
FLUX_ACCESS_PASSWORD / FLUX_ACCESS_USERNAME	none / flux	Optional HTTP Basic gate for private deployments.
FLUX_MAX_CONCURRENT	2	Simultaneous jobs on the whole server.
FLUX_MAX_FILESIZE	4G	Largest single file fetched.
FLUX_MAX_DURATION	7200	Maximum source duration in seconds.
FLUX_MAX_JOB_BYTES	4294967296	Aggregate temp bytes per running job.
FLUX_RETENTION_HOURS	24	How long finished files are kept.
FLUX_INSPECT_PER_10MIN	40	Link lookups per visitor per 10 minutes.
FLUX_JOBS_PER_HOUR	15	Jobs started per visitor per hour.
FLUX_ACTIVE_PER_VISITOR	6	Queued + running jobs per visitor.
FLUX_TRUST_PROXY	0	Trust X-Forwarded-For. Enable only behind a proxy that overwrites it.
FLUX_EXTRA_SOURCE_HOSTS	none	Extra reviewed source hostnames (comma-separated).
FLUX_DATA_DIR	./data	Private state: jobs, sessions, temp media.
YTDLP_PATH, FFMPEG_PATH	auto	Override tool locations.

Setting up Google sign-in

Flux uses Google's server-side OAuth authorization-code flow with the official google-auth-library. No Supabase or separate auth service is needed.

1. In Google Cloud → Google Auth Platform, configure the consent screen (name, support email, audience; add test users while in testing).

2. Create an OAuth client of type Web application.

3. Register the exact redirect URI:

   • Local: http://localhost:3000/auth/google/callback
   • Production: https://YOUR_DOMAIN/auth/google/callback

4. Set the server-only variables:

   FLUX_ORIGIN=https://YOUR_DOMAIN
   GOOGLE_CLIENT_ID=your-web-client-id
   GOOGLE_CLIENT_SECRET=your-client-secret

5. Restart Flux, then sign in, refresh, sign out and test cancellation.

Use one canonical hostname: localhost and 127.0.0.1 do not share cookies. Without credentials the sign-in dialog says so honestly and shows no fake button.

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🏗 Architecture

flowchart LR
    B["Browser<br/>(plain ES modules)"] -->|"cookie session + X-Flux-Token"| S["Node HTTP server<br/>server.mjs"]
    S --> A["lib/auth.mjs<br/>Google OAuth, sessions"]
    S --> P["lib/platforms.mjs<br/>source allowlist"]
    S --> M["lib/media.mjs<br/>format selection, validation"]
    S -->|spawn| Y["media engine"]
    Y -->|"all HTTP(S)"| E["lib/egress.mjs<br/>loopback egress proxy<br/>DNS pin, public IPs only"]
    E --> I(("Internet"))
    S -->|spawn| F["FFmpeg / FFprobe<br/>preview + validation"]
    S --> D[("FLUX_DATA_DIR<br/>jobs.json, sessions.json,<br/>per-job temp dirs")]

Loading

The download pipeline:

Source input → URL validation → metadata → selection → verified session → owned job → extraction → preview / full processing → private file delivery → history

Project layout

flux/
├── server.mjs            HTTP server, routing, job queue, rate limits
├── lib/
│   ├── auth.mjs          Google OAuth (PKCE, state, nonce), sessions, CSRF
│   ├── egress.mjs        SSRF-safe loopback proxy for extractor traffic
│   ├── media.mjs         engine argument builder, format rules, validation
│   └── platforms.mjs     Supported source families
├── public/               Static front end (no bundler)
│   ├── index.html · styles.css · app.js · api.js · components.js · icons.js
├── scripts/              setup, syntax check, screenshots, icon generation
├── test/                 node:test unit/integration + Playwright + axe suites
├── docs/screenshots/     README images
├── Dockerfile · compose.yaml · Caddyfile
└── .github/              CI, issue forms, PR template, Dependabot

Design decisions:

• Zero build step. public/ is served as-is. Edit, refresh, done.
• Two runtime dependencies: google-auth-library and ipaddr.js. Everything else is the Node standard library.
• Single process, single volume. JSON state with atomic replacement keeps self-hosting trivial. Don't run multiple instances on one data directory; move to a database and shared queue before scaling horizontally.

API

All POST endpoints require the session's X-Flux-Token CSRF header.

Endpoint	Purpose
GET /api/session	Guest/account session, CSRF token, Google config status, retention
GET /auth/google · /auth/google/callback	Start / complete OAuth
POST /api/logout	Revoke session, issue a fresh guest session
POST /api/inspect	{url, playlist?} or {search} → real metadata/results
POST /api/jobs	{items:[{url}], mode:"preview"|"full", authorized:true, options}
GET /api/jobs	The current owner's jobs only
POST /api/jobs/:id/cancel · /retry	Cancel an active job / regenerate a failed or expired one
GET /api/jobs/:id/files/:index	Private, cookie-authenticated file stream (range-enabled)
POST /api/jobs/clear	Remove the owner's finished records and files
GET /api/health	Actual media engine / FFmpeg availability
GET /api/platforms	Source-family directory

options: format (mp4/mp3), quality (best or a resolution cap), bitrate (128/192/256/320), subtitles, language. Job states: queued, processing, downloading, completed, failed, cancelled, expired.

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🔒 Security model

Flux is designed to be exposed to the internet, so security is a core feature, not an afterthought.

• Server-side OAuth with state + PKCE + nonce. The ID token's signature, audience, issuer, expiry and email_verified are all checked. Only openid email profile are requested, and Google access/refresh tokens are never stored.
• Sessions: opaque tokens stored hashed, HttpOnly, SameSite=Lax, Secure over HTTPS, rotated on login/logout, 7-day expiry, per-session CSRF tokens.
• Authorization on every object: jobs, lists, retries, cancels, clears and file delivery are checked against the session owner. Full downloads require a verified account. Browser-supplied identity fields are ignored.
• SSRF protection: extractor traffic goes through a loopback-only egress proxy that validates DNS results and pins a public IP per connection, including redirects. Private, loopback, link-local, reserved and IPv4-mapped addresses are refused.
• Argument-injection safe: URLs are passed as separate spawn arguments after --. No credentials or custom ports in source URLs, and no arbitrary extractor arguments are accepted.
• FFmpeg sandboxing: preview processing is limited to local file, data and crypto protocols.
• Resource limits: duration, per-job bytes, file size, concurrency, per-visitor and per-IP rate limits, and an aggregate disk guard.
• No public file serving: media is only reachable through authenticated streams, never held fully in memory.

Found a vulnerability? Please follow SECURITY.md and do not open a public issue.

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🌐 Deployment

cp .env.example .env
# set FLUX_PUBLIC_HOST, GOOGLE_CLIENT_ID/SECRET, and FLUX_PUBLIC_OPEN=1 (or a password)
docker compose up -d --build

1. Point your domain's A/AAAA record at the server (ports 80 and 443 open).
2. Caddy obtains and renews TLS certificates automatically.
3. Register https://YOUR_DOMAIN/auth/google/callback in Google Cloud.
4. The PO-token provider (flux-pot) stays on the internal Docker network. Never publish its port.
5. The Flux container includes a Docker healthcheck for /api/health; use docker compose ps to verify that it becomes healthy after startup.

Operator notes. YouTube may still block datacentre IPs or require extra checks, and a token provider is no guarantee. Keep the media engine and FFmpeg updated (rebuild the image regularly), apply container filesystem quotas, and add outbound firewall rules as defence in depth. The optional cookies file is sensitive and must never be served. The shared Basic-auth password is only an outer gate and does not grant full-download privileges.

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🧪 Development & testing

npm run check          # parse every module
npm test               # unit + integration (incl. real FFmpeg tests)
npm run format:check   # Prettier

# with the server running:
npx playwright install chromium
npm run test:browser   # end-to-end workflow, responsive checks
npm run test:a11y      # axe-core WCAG A/AA
node scripts/screenshots.mjs   # regenerate README screenshots

What the suite covers: URL validation, format selection, session rotation/persistence/revocation, OAuth state/nonce verification, CSRF, guest-full denial, cross-owner isolation, blocked internal destinations, real FFmpeg preview generation (a 600 s video → ~300 s, a 240 s audio → ~120 s, fully decoded), 18 responsive page checks and axe scans.

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🗺 Roadmap

Ideas welcome via issues. Current thinking:

• SQLite storage and a shared queue for multi-instance deployments
• Optional additional OAuth providers
• Thumbnails in lookup results and the library
• Light/dark preference toggle independent of source theming
• Internationalisation
• Prometheus metrics endpoint

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🤝 Contributing

Contributions of every size are welcome: bug reports, docs, tests, new ideas and code. Start with CONTRIBUTING.md and look for issues labelled good first issue. Everyone participating is expected to follow the Code of Conduct.

Contributors are welcome, human or AI. Coding agents should start with AGENTS.md (code map, commands, rules) and llms.txt. Work goes through forks and pull requests.

⚖️ Responsible use

Flux is a tool. You are responsible for how you use it. Only save media you own, that is licensed for it, or that you have permission to download, and respect the terms of service of each platform and the copyright law where you live. Flux asks every user to attest to this on each request, but that attestation is not an automated copyright determination. The maintainers do not host, index or distribute any media, and do not endorse infringement. Spotify links are used only for metadata (to search a match); Flux never extracts Spotify audio.

🙏 Acknowledgements

FFmpeg · PO token provider · Caddy · Playwright · axe-core. Platform marks come from Simple Icons (CC0); the RadioJavan mark is from its official site. Trademarks belong to their respective owners.

📄 License

MIT © Lokii. Built by lokii.dev.

_{If Flux is useful to you, a ⭐ helps others find it.}