Firefox Browser Add-ons
  • Extensions
  • Themes
    • for Firefox
    • Dictionaries & Language Packs
    • Other Browser Sites
    • Add-ons for Android
Log in
Preview of KoalaSync

KoalaSync by HungryKoala

Watch party extension to synchronize video playback on YouTube, Twitch, Netflix, and HTML5 sites in real-time with friends.

0 (0 reviews)0 (0 reviews)
Download Firefox and get the extension
Download file

Extension Metadata

Screenshots
About this extension
KoalaSync: The Privacy-First Watch Party Extension

Synchronize movies, series, and videos in real-time with friends—no accounts, no tracking, no lag.

Whether you're binge-watching Netflix, catching a Twitch stream, or using custom self-hosted platforms like Emby, Jellyfin, and Plex, KoalaSync keeps everyone perfectly in sync. Lightweight, open-source, and built for absolute data sovereignty.

✨ CORE FEATURES
• Universal HTML5 Sync: Flawlessly synchronize play, pause, and seeking on YouTube, Netflix, Disney+, and virtually any website with a standard video player.
• Smart Binge-Watching (Auto-Sync): The ultimate series coordinator. When a new episode loads, KoalaSync automatically pauses playback in a smart lobby until everyone’s video is ready. No spoilers, no one left behind.
• One-Click Invitations: Generate a smart invite link. Once your friends click it, their extension instantly configures the room credentials and server settings.
• Zero-Latency Protocol: Powered by a custom WebSocket architecture designed for frame-perfect, real-time coordination without buffering loops.

🛡️ UNCOMPROMISING PRIVACY
Built by developers who care about security. We don't want your data.
• 100% Anonymous: No accounts required, no tracking, and zero analytics.
• Zero Persistence: Our official public relay server operates entirely in volatile RAM. No databases, no logs, no watch history.
• Self-Hostable: Take total control. Deploy your own private relay server in seconds using Docker and connect your extension with a single click.
• Pure Performance: Built with clean, dependency-free Vanilla JS to keep your browser fast and resource-friendly.

🚀 HOW IT WORKS (IN 3 SECONDS)
• Open the KoalaSync popup and pick a nickname.
• Click "Create Room" and copy the invite link.
• Send the link to your friends, start a video, and watch together perfectly synced!

💻 OPEN SOURCE & SUPPORT
KoalaSync is completely free, open-source, and MIT-licensed.
Want to self-host, audit our code, or contribute? Visit us on GitHub:
https://github.com/Shik3i/KoalaSync
Rated 0 by 0 reviewers
Log in to rate this extension
There are no ratings yet

Star rating saved

5
0
4
0
3
0
2
0
1
0
No reviews yet
Permissions and data

Required permissions:

  • Display notifications to you
  • Access browser tabs
  • Access your data for sync.koalastuff.net

Optional permissions:

  • Access your data for all websites

Data collection:

  • The developer says this extension doesn't require data collection.
Learn more
More information
Add-on Links
  • Homepage
  • Support site
  • Support Email
  • Copy add-on ID
Version
1.5.1
Size
74.24 KB
Last updated
4 days ago (May 18, 2026)
Related Categories
  • Photos, Music & Videos
  • Tabs
License
MIT License
Privacy Policy
Read the privacy policy for this add-on
Version History
  • See all versions
Tags
  • streaming
  • twitch
  • youtube
Add to collection
Report this add-on
Go to Mozilla's homepage

Add-ons

  • About
  • Firefox Add-ons Blog
  • Extension Workshop
  • Developer Hub
  • Developer Policies
  • Community Blog
  • Forum
  • Report a bug
  • Review Guide

Browsers

  • Desktop
  • Mobile
  • Enterprise

Products

  • Browsers
  • VPN
  • Relay
  • Monitor
  • Pocket
  • Bluesky (@firefox.com)
  • Instagram (Firefox)
  • YouTube (firefoxchannel)
  • Privacy
  • Cookies
  • Legal

Except where otherwise noted, content on this site is licensed under the Creative Commons Attribution Share-Alike License v3.0 or any later version.