Last updated: September 26, 2026
Seamless Sync is a free, non-commercial Chrome/Edge extension that lets two people watch a YouTube video together in sync over a direct peer-to-peer connection. This policy explains what happens to your data when you use it.
Seamless Sync does not collect, store, sell, or transmit any user data to its developer or to any third-party server operated by the developer. There is no backend, no account system, no analytics, and no advertising in this extension.
Playback data (video selection, play/pause/seek/speed). When you're in an active session, this information is sent directly to the other participant over an encrypted, direct WebRTC connection (peer-to-peer). It is never sent to, or stored on, any server the developer operates. It exists only for the duration of the session and is discarded when the session ends.
Connection setup metadata. To establish that direct peer-to-peer connection, Seamless Sync uses:
PeerJS's free public pairing service (0.peerjs.com), which briefly relays connection-setup information so the two browsers can find each other.
Google and Cloudflare public STUN services, which help the two browsers establish a direct connection through typical network configurations.
These third-party services are not operated or controlled by the developer, and see limited connection metadata (such as IP addresses) as an inherent part of how WebRTC connections are established - the same way any peer-to-peer or video-calling technology works. No paid fallback or TURN relay is used, and once the direct connection is established, both connections to the pairing service close.
IP address visibility. Because the connection is direct (peer-to-peer), the person you're syncing with can see your public IP address, and vice versa - this is inherent to how WebRTC works, not something Seamless Sync separately collects or logs. The pairing and STUN services above also see IP addresses only as needed to establish the connection.
Invite links. When you create an invite, the extension generates a link containing a random session key. This key lives in the URL fragment (the part after #), not in the query string, and the extension removes it from the address bar once a join begins. You choose how to share this link (e.g., via your own messaging app) - Seamless Sync does not send it anywhere on your behalf, and does not read your clipboard. It only writes the invite link to your clipboard after you click to copy it.
Video and ad content. Each participant's browser loads video and ad content directly from YouTube, as it normally would. Seamless Sync does not proxy, relay, record, or have access to this content.
Local/session storage. Settings and temporary session identifiers (such as the active invite or session state) are kept only in temporary session storage on your own device and are not transmitted to the developer.
No account creation or login
No collection of personally identifiable information (name, email, address, etc.)
No analytics, tracking, or advertising SDKs
No chat, messaging, or communications relay
No browsing history collection
No microphone or camera access
No server operated by the developer that stores or processes your data
Starting with version 4, all sync messages between the two participants are encrypted and authenticated using AES-GCM with a random key generated for that invite. This key is never included in the connection-setup metadata sent through the pairing service. Messages are bound to the session and sender, and sequence numbers are used to reject replayed messages.
This encryption protects the content of what's being synced. It does not hide network-level identifiers: as noted above, your peer and the pairing/STUN services can still see IP addresses and connection metadata, as with any direct peer-to-peer connection.
Seamless Sync does not knowingly collect data from anyone, including children, because it does not collect data at all.
If this policy changes - for example, if a future version adds functionality that touches user data - this document will be updated and the "Last updated" date above will change accordingly.
Questions about this policy can be directed to: LuweDeveloper@gmail.com