Privacy and terms
SameTube lets a few people watch YouTube videos at the same time. This page says what it keeps and what you agree to by using it.
No accounts
There is nothing to sign up for. When you join a room you pick a display name, and your browser makes up a random token so the room can recognise you if you come back. Both live in your browser's site data; clear it and they are gone.
What the server keeps
For each room, while it exists: the video and queue (YouTube video IDs and titles), the display names and tokens of everyone who has been in it (including after they leave, so they can rejoin as the same person), who has control, who has been removed, and where playback is. This is written to disk so rooms survive a restart, and it is deleted ten minutes after the last person leaves. There are no advertising trackers and no analytics scripts. The server does keep daily totals for 90 days (rooms created, people joining, videos queued, and the busiest moment of the day) so the person running it can tell whether anyone uses it; those totals are not tied to a person, a room, or an address.
The server holds your IP address in memory briefly to limit how many rooms one address can create per hour and how often it can search. The hosting proxy keeps ordinary access logs (IP address, time, and the page requested, which includes the room code).
Search
If search is enabled, the text you type into the add box is sent to YouTube's search service and results are cached on the server for a day. Your name is not attached to it.
Videos
Videos play in YouTube's own embedded player under YouTube's terms of service and privacy policy. SameTube does not host, copy, or alter any video.
Using it
SameTube is a small, free service provided as-is, with no guarantee it will be available or that a room will not be lost. Do not use it to share anything you would not be comfortable showing to everyone in the room. The host of a room can remove people from it.
Questions
Ask whoever shared this site with you; it is run by an individual, not a company.