Good questions.

1. Download the app: sign up free, then get the Mac beta or the Windows test on Download.
2. Install: unzip it and open DJ back 2 back. On a Mac, move it to Applications first. On Windows, it's in the folder the zip makes.
3. Set up your sound: log in, then pick your DJ software, your controller and a partner level. On a Mac, allow what macOS asks for the first time, so the other DJ hears your mix.
4. Find a DJ to play with: find one on Live and link up, or invite a DJ you know.
5. Go back to back: join from Your sessions in the app, mix, and press Handover when it's their turn.

Two DJs, two places, one set.
Play your own gear, mix on your own gear. Hand audio and control over, listen on your gear and wait for the hand back. Hit Handover, they hit Accept, and the set is theirs.

A Mac for the beta app, or a Windows PC for the early Windows test. Then a laptop controller with its DJ software, headphones, and the internet. A club mixer on USB, such as a Pioneer DJM, works too.

You need macOS 14.2 or later on a Mac, or Windows 11 (64-bit) on a PC.

As an early test.

The beta app isn't from the App Store or a registered developer, so the first time, macOS asks you to confirm it once. On macOS 15 or later: open it, and when macOS says it can't verify it, click Done. Then open System Settings → Privacy & Security, scroll down, click Open Anyway, and then Open. On macOS 14: right-click it, choose Open, then click Open.

The test app isn't signed yet, so turn Smart App Control off first (Windows Security, then App & browser control, then Smart App Control). When Windows says it protected your PC, click More info, then Run anyway.

It's built for rekordbox, Serato and VirtualDJ on a laptop controller, and we're testing each one now. VirtualDJ can also bring your partner onto a deck through its line input; that may need a paid VirtualDJ licence. In rekordbox and Serato you bring your partner up with the app's Partner level instead.

60 minutes as standard, minimum 30 minutes. You see the length when the code is made, before you start, and it's kept. When it's reached, you're both told time's up, and you get 2 minutes to finish your track before the session closes.

60 minutes as standard, minimum 30 minutes. The app shows the length before you start, and it's kept. When it's reached, you're both told time's up, and you get 2 minutes to finish your track before the session closes.

Free during the beta. After the beta, DJ back 2 back will be priced from £4.99 a month (or the local equivalent), up to an unlimited plan. Beta accounts work through the beta and a short transition after it. After that, you can't start or join sessions unless you're paying. Your login and profile stay.

In our tests the other DJ's mix reaches you about 0.1 seconds after they play it (about 100 ms, measured through Cloudflare's relay on one connection in England). Between two homes it depends on the distance and your internet; real figures follow from the beta.

When you take over, your partner hears the music jump by about 0.2 seconds; you hear little or none.

A steady one. In our tests the link held at a 200 ms round trip. At 1% packet loss you hear short gaps, and at 3% it breaks up. A cable or strong Wi-Fi is best.

A mic on your controller isn't sent if your controller mixes the mic in its own hardware, after your DJ software. The Pioneer DDJ-FLX6, Numark Mixtrack FX and Hercules Inpulse T7 work that way.

You hear your partner about 0.1 seconds late (more between distant homes), so mix in by ear.

Your connection matters. Losing about 1 packet in 100 is heard as small gaps. From about 3 in 100, mixing in doesn't work.

Usually a network in the way: some home and mobile networks won't link directly, and a VPN can block it. Check you're both logged in, typed the same code, and both pressed Connect. Give it 30 seconds. If the app says "Couldn't connect, even through the relay", try again with one of you on a different network and any VPN off. A link-up that fails costs no session.

Usually a network in the way: some home and mobile networks won't link directly, and a VPN can block it. Check you're both logged in with your DJ software open, and that one of you accepted the other's invite or opened their link. If you sent the invite, accepted it or made the link on the site, press Join under Your sessions in the app. Give it 30 seconds. If the app says "Couldn't connect, even through the relay", try again with one of you on a different network and any VPN off. If it says "Couldn't reach the relay", try again in a minute. A link-up that fails costs no session.

Post the recording on YouTube, SoundCloud, Facebook, Instagram or Twitch and it can get muted, blocked or pulled, and enough strikes cost you the account. Put it on Mixcloud: it pays the artists you play, so your mix stays up. The steps are on our copyright page.

The Top 10: the sets members liked most in the last 7 days, or in the last 30 when the week is quiet. You can't like your own set. A tie goes to the set with more Listen presses.

Your mix goes to the other DJ over an encrypted link: your DJ software's sound (on a club mixer, the channels that carry your own decks) and nothing else. We don't record it. When you link up by an invite by DJ name or a link, it goes straight to your partner, or through Cloudflare's relay when your networks need one, and they get your internet address, so the two apps can connect directly. When you link up from Live, it goes through Cloudflare's relay, so they don't. A practice sends your mix through Cloudflare's relay and back to you, and we don't record that either.

Everything we keep is listed on our privacy page.

Up to 3 genres you pick on your account are kept whether your public page is on or off. Live matches you on them. You can turn that off on your account page. Your public page, if you turn it on, shows your DJ name, those genres, a verified Mixcloud link and the b2b sets you list; never your email, your library or your sessions.

If you delete your account, we remove your email, DJ name, bio, kit, password, logins, library profile, the genres you picked, invites and share links, your Live status and blocks, your Mixcloud link, your board ban, the record of account emails we sent you (a security notice's record stays 3 years, with our breach log), your rate-limit counts, your practice times, your live link, the likes you gave, and the sets on Mixes whose show is on your own Mixcloud account, with their likes and Listen totals. Your public page goes off and its address is retired, so it's never given to anyone else. Your past sessions and purchases stay, shown under 'Deleted DJ' with no email, and so does a set your partner put on their own Mixcloud; your board posts and topic titles are replaced with '[removed]', and any words you added to a board report are deleted. Purchases keep the payment reference, and Stripe keeps its own payment record. A request you sent us about your data is kept for 24 months, so we can show we answered it.

Any issues? Email support@djb2b.com

If the app's playing up, send us the newest djb2b-<date>.jsonl file (or djb2b.jsonl on older versions). On a Mac, in Finder, choose Go → Go to Folder and enter ~/Library/Application Support/djb2b-app/. On Windows, enter %APPDATA%\djb2b-app\ in File Explorer's address bar.