WatchSync

Project Overview

WatchSync is a Windows desktop app built on Tauri 2 and WebView2 for watching the same web video in sync with friends who are far away. It opens video pages (such as Bilibili, Ciyuancheng and any site containing a video element) in a built-in browser, establishes peer-to-peer connections between viewers over WebRTC, and lets the host drive playback while everyone else follows automatically. The whole approach needs no server deployment and no account registration, using public relays only for signaling.

A serverless watch-together tool: the host presses play and everyone follows.

Key Features

• Zero server: signaling uses public relays, and once connected all data flows over direct WebRTC
• One-tap invite: the host creates a room and generates an invite link that others can copy and paste to join
• Any web video: the built-in browser opens pages and injects scripts to locate and control the video element
• DRM support: the built-in browser ships a Widevine component, enabling playback of encrypted content
• Hardware decoding: shares the Edge media stack for hardware decoding of H.264, HEVC, VP9 and AV1 by system capability
• Host authority: the host's play, pause and seek operations broadcast in real time while members' local actions are intercepted
• Direct calibration: a heartbeat every two seconds realigns playback when the drift exceeds a threshold
• Room management: member list, nicknames, live latency, host transfer and leave
• Relay probing: automatically probes usable signaling relays at startup and reuses them persistently
• Multi-tab browsing: multiple web tabs, a custom title bar and adaptive full screen for web video

Target Audience

• Users who want to watch videos with friends in different places
• Windows desktop viewers
• Users who prefer not to register accounts or rely on third-party sync platforms
• Users who care about privacy and direct connections

Quick Start

Host

1. Tap a site card on the home page or type a video page address in the address bar and press Enter
2. Click Create Room
3. Click Copy Invite and send the link to others

Member

1. Click the invite link you receive, or paste it into the paste-invite box
2. After joining, the video opens automatically and jumps to the host's position
3. When the host plays, pauses or seeks, members follow automatically

Core Advantages

• No server needed: no backend to deploy and no account to register; just open and use
• Peer-to-peer: once connected, data flows over direct WebRTC for better privacy
• Strong compatibility: the built-in browser opens any page with a video element and supports DRM and hardware decoding
• Precise sync: host-driven authority plus heartbeat calibration keep progress aligned

System Requirements

Item	Requirement
OS	Windows 10 / 11 (x64)
Runtime	WebView2 Evergreen runtime
Dev environment	Node.js 18 or later and Rust stable
Network	Reaching public signaling relays is required to connect

Notes

• Symmetric NAT: when both sides are behind symmetric NAT, hole punching may fail; there is no relay fallback yet, and the UI shows a warning
• Embedded players: currently the app mainly supports sites with a direct video element on the main page; sites with embedded iframes are still being adapted
• Usage boundary: for personal learning and technical research only; follow the terms of service and copyright rules of the sites you visit
• Site adapters: adding a new site requires implementing and registering its adapter in the source