DuoDub

Privacy, in plain words

Updated 28 September 2026.

DuoDub lets two people watch the same film in two languages, each in their own headphones. This is everything it touches, and everything it doesn’t.

What DuoDub does

It presses the streaming site’s own play, pause and seek controls, and it tells Chrome which headphones each window should play through. That is all it does to the film.

It never records, copies, captures or re-sends the picture or the sound, and it never gets around copy protection. No audio or video ever leaves your browser.

The microphone

Chrome hides the names of your headphones from websites until the microphone is allowed. DuoDub asks for it only so that Chrome will show those names, and turns the microphone off the moment they appear. Nothing is recorded, listened to or sent anywhere.

What the two windows tell each other

To stay together, your two windows send each other short control messages. That is all they send:

• play, pause, and the position in the episode
• which title and episode is playing: its Netflix address (without anything after the ?) and its name
• the Netflix profile name in each window, such as “Anna”
• the names of your headphones, such as “AirPods Pro”
• the languages a title offers and the one each of you chose, as codes such as “en” or “ru”
• requests between the windows, such as “play the test sound” or “open this episode”
• a few technical facts for keeping in step: how far apart the windows are, the DuoDub version, how many Netflix pages are open, and how far setup has got

They never contain sound, pictures, passwords or your viewing history.

How the messages travel

They go through a relay: Supabase Realtime, a message service run by Supabase in the European Union (Frankfurt). It passes each message straight on to the other window and does not keep it. Like any internet service, Supabase sees the internet address each window connects from, and keeps ordinary server logs under its own privacy policy.

Every message is signed with a key that only your two windows know. The relay could read what a message says, which is only the list above, but nobody without the key can change a message or fake one, so nobody else can press play or pause in your windows.

The pairing link

The link you copy in the first window carries that key after the # sign. Browsers keep everything after # to themselves and never send it to a server, this website included. The pairing page only checks that the link arrived whole. It has no analytics, sets no cookies, and loads nothing from anywhere else. A window that is already paired never switches to another pairing from a link; you forget the old pairing first.

If you pair with the six-digit number instead, the first window hands the key, once, to the first window that types the number, through the relay. The number stops working when your windows are paired, or after ten minutes.

What stays on your computer

DuoDub keeps its settings in Chrome on your computer: the key, the headphones and language each of you chose, and how far setup has got. “Forget this pairing” in Details removes the key. Removing DuoDub from Chrome removes everything.

Asking for help

“Copy a report for support” in Details puts technical facts about your two windows on your clipboard, without names, titles or headphone names. Nothing is sent unless you paste it into a message to us yourself.

No accounts, no tracking

There is nothing to sign up for. DuoDub has no analytics, no advertising and no tracking. We keep no record of what you watch, and we sell or share nothing.

Questions

Write to privacy@example.com.