KoalaSync

What it does

KoalaSync perfectly synchronizes video streams across multiple devices. It works universally with Netflix, YouTube, and any HTML5 player, but was specifically built to support self-hosted servers like Emby, Jellyfin and Plex. No accounts, no tracking. Features include TV show auto-syncing and smart tab matching. It's 100% free, open-source, and you can even self-host the WebSocket relay server for complete data privacy.

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  Hi HN! I made Beatsync, an open-source browser-based audio player that syncs audio with millisecond-level accuracy across many devices. Try it live right now: https://www.beatsync.gg/ The idea is that with no additional hardware, you can turn any group of devices into a full surround sound system. MacBook speakers are particularly good. Inspired by Network Time Protocol (NTP), I do clock synchronization over websockets and use the Web Audio API to keep audio latency under a few ms. You can also drag devices around a virtual grid to simulate spatial audio — it changes the…

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