Stream your Steam Deck screen to any browser.
Hardware accelerated, one-tap start from Game Mode.

Showcase

How It Works

Steam Deck (Game Mode)
┌────────────────────────────────────────────────────────┐
│                                                        │
│  Gamescope → kmsgrab → FFmpeg (VAAPI H.264)            │
│                            │                           │
│                    ┌───────┴────────┐                  │
│                    │                │                  │
│              MPEG-TS HTTP      MediaMTX RTSP           │
│              (stream_server)   (WebRTC relay)          │
│                    │                │                  │
│                 :7770            :8889                  │
│                                                        │
│  Decky QAM: [Start Streaming] Quality Method           │
└────────────────────┬───────────────┬───────────────────┘
                     │               │
              ┌──────▼──────┐ ┌──────▼──────┐
              │ mpegts.js   │ │ WebRTC      │
              │ ~500ms      │ │ ~200ms      │
              │ Any browser │ │ Any browser │
              └─────────────┘ └─────────────┘

Features

• One-tap streaming from Steam Deck QAM (Quick Access Menu)
• Two streaming methods:
  • MPEG-TS - stable, ~500ms latency, works everywhere
  • WebRTC - lower latency ~200ms via MediaMTX
• VAAPI hardware encoding - H.264 on AMD GPU, near-zero CPU usage
• Quality presets - 480p30, 720p30, 720p60, 1080p30, 1080p60
• Live stats - viewers, bytes sent, encoder status in QAM
• Auto-restart - recovers from capture failures
• No Desktop Mode required - works entirely in Game Mode

Install

From Decky Plugin Store

Search for Prysm in the Decky plugin store (coming soon).

Manual Install (one-liner)

curl -sL https://raw.githubusercontent.com/hostsrc/decky-prysm/main/install.sh | bash

From ZIP

Download Prysm-v0.2.0.zip from Releases, extract to ~/homebrew/plugins/, restart Decky.

Usage

1. Open a game on your Steam Deck
2. Press ... (QAM button)
3. Find Prysm in the plugin list
4. Choose Method (MPEG-TS or WebRTC) and Quality
5. Tap Start Streaming
6. Open the URL on any device on the same network

Requirements

• Steam Deck running SteamOS 3.5+
• Decky Loader installed
• FFmpeg with VAAPI (pre-installed on SteamOS)
• Game must NOT have ENABLE_GAMESCOPE_WSI=0 in launch options

QAM Panel

PRYSM
┌─────────────────────────────┐
│ [Start Streaming]           │  ← one tap
│ Status: Ready               │
│ Method: MPEG-TS (~500ms)  ▾ │
│ Quality: 720p 30fps       ▾ │
│ Audio: [on]                 │
└─────────────────────────────┘

When streaming:
┌─────────────────────────────┐
│ [Stop Streaming]            │
│ Status: Streaming           │
│ URL: http://192.168.1.50:.. │
│ Viewers: 1                  │
│ Sent: 56.2 MB              │
│ Encoder: Active · 720p30   │
└─────────────────────────────┘

Performance

Tested on Steam Deck with Hades over WiFi and Ethernet:

Metric	720p30	1080p30
Bitrate	~5 Mbps	~8 Mbps
Decoded FPS	29 fps	29 fps
Dropped frames	<1%	~4%
Buffer	0.4s	0.4s
CPU usage	<3% (VAAPI)	<3% (VAAPI)

Development

# Clone
git clone https://github.com/hostsrc/decky-prysm.git
cd decky-prysm

# Install deps
pnpm install

# Build
make build

# Deploy to Steam Deck
make deploy DECK_IP=192.168.88.197

# Create distribution zip
make dist

Project Structure

decky-prysm/
├── src/                        # Decky frontend (TypeScript/React)
│   ├── index.tsx               # Plugin root
│   ├── components/
│   │   └── ViewerPanel.tsx     # Main streaming panel
│   ├── hooks/
│   │   └── usePrysmStatus.ts   # Status polling
│   └── lib/backend.ts          # Typed backend callables
├── main.py                     # Decky Python backend
├── server/
│   └── stream_server.py        # MPEG-TS HTTP server
├── backend/
│   ├── mediamtx.yml            # MediaMTX WebRTC config
│   └── prysm-engine/           # Rust streaming engine (future)
├── bin/
│   └── mediamtx               # MediaMTX binary (WebRTC mode)
├── dist/index.js               # Built frontend bundle
├── plugin.json                 # Decky plugin metadata
├── package.json
├── Makefile                    # build/dist/deploy commands
├── install.sh                  # One-liner installer
└── LICENSE                     # GPL-3.0-or-later

Roadmap

• MPEG-TS streaming with mpegts.js viewer
• WebRTC streaming via MediaMTX
• VAAPI hardware H.264 encoding
• Quality presets (480p → 1080p60)
• Live stats in QAM
• Auto-restart on capture failure
• Decky Plugin Store distribution zip
• Audio streaming
• Native PipeWire capture (replace kmsgrab)
• Native Rust streaming engine
• QR code for mobile viewer
• Discord Go Live automation

License

This project is licensed under the GNU General Public License v3.0 (GPL-3.0).

The Decky Plugin Template portions are licensed under BSD-3-Clause (see full LICENSE file).

What GPL-3.0 means for you

If you just use Prysm - do whatever you want, it's free.

If you fork or modify Prysm - you must:

• Keep the source code open (you can't make it proprietary)
• Include this same GPL-3.0 license
• State what you changed

If you distribute Prysm - same as above, plus you must provide the source code.

In short: you can use, study, modify, and share it freely - but you can't close-source it. Anything built on Prysm stays open.