Privacy Policy
- No account, no sign-up, no ads of our own, no analytics, no advertising ID, no location.
- No SynkEngine server. The app sends nothing about you or your music to us.
- A party runs on your own Wi-Fi or hotspot: your phone talks to the other phones in it, and that traffic stays on that network.
- The app also talks to YouTube, SoundCloud and a lyrics service, directly and under their own privacy policies (section 5). The Google Play version does not search or browse YouTube by itself: it only asks about the songs in your party and in your own lists.
- The microphone is used to sync the phones, for karaoke and the mic test, and on the host to find a song's beat. The sound never leaves the phone, except a karaoke singer's voice: that goes live to the party's phones and is never recorded.
- What the app keeps is on your phone, and uninstalling removes it. Other phones in your parties can keep your name in their logs.
1. Who we are
SynkEngine is made by Kavish Moosoohur, an independent developer in Mauritius, who is responsible for the app and for this policy. Contact: kavish.m@hotmail.com.
2. What the app keeps on your phone
These stay in the app's private storage on your phone. Other apps cannot read them, and the app does not include them in Android's cloud backup.
| What | Why |
|---|---|
| Your display name | So the other phones can show who is who. You choose it; until you do, it is a stage name the app makes up. |
| A random app ID | 16 random characters made when the app first runs, so the party can tell the phones apart. It is not linked to you, your phone number or your Google account. |
| Your Phone ID | A short code worked out one way from Android's identifier for this phone (on Android 8 and later, an identifier Android gives this app alone), so a licence can be made for this phone only. The app shows it to you and never sends it anywhere. |
| That you accepted the terms | The version of the terms of use you agreed to, so the app asks again only when they change. |
| Sync memory | How late this phone's speaker and earphones run, the timings learned in past rounds, and what the phones learned about other phone models, so the next party starts in step. |
| Recent and saved songs | Titles and links of what you played and saved, for the lists on the first screen. In the Google Play version, "Keep the music going" picks from these (section 5). |
| Song pictures | The YouTube thumbnail of each song in your lists, so a list shows without the internet. The Google Play version keeps each one 30 days at most, then fetches it again or deletes it. |
| Hosting time and licence | The 40 free minutes of hosting, and a licence key if you enter one. Keys are checked on the phone, without the internet. |
| Songs shared in a party | When a phone in your party shares a song from its storage, your phone keeps a copy in the app's private cache to play it in step. The sharing phone keeps its own copies there too. When the app starts, it trims the cache to about 400 MB, oldest files first, and Android may also clear it. |
| Diagnostic logs | A record of the app's sync and network decisions and of crashes, plus a field log that is on by default. The field log grows across sessions until it reaches 12 MB, then stops writing; you can stop or restart it on the app's Sync log screen. The logs hold the names, phone models and app IDs of the phones in your parties, song titles and links, timings, network figures, and whether a phone stepped out (for a call, by a tap, or because its app was not on screen). They never hold a licence key or code, and they leave the phone only if you send them yourself (section 7). |
| Web data | The cookies and storage that YouTube's and SoundCloud's players keep in the app's player. In the version from synkengine.com only, also those of YouTube's and SoundCloud's pages opened in the app's built-in browser, including a YouTube sign-in if you choose to sign in there. The Google Play version has no built-in browser: links open in the YouTube app or your browser. |
To delete all of it: uninstall the app, or open Android Settings → Apps → SynkEngine → Storage → Clear storage.
3. What goes to other phones on your network
Phones in a party talk directly to each other over the Wi-Fi network or hotspot they share. None of this goes to us or to the internet.
| What | Who receives it | How long |
|---|---|---|
| While you host: your display name, announced as "SynkEngine-your name" | Every device on the network (through the network's service discovery, mDNS), and any phone that searches for parties | While you host |
| Your display name, random app ID, phone model, app version and local network address | The phones in your party. The phone model chooses timing settings, and the app version shows when a phone needs an update. | For the party. Other phones' logs can keep them (section 2). |
| The party's name | Phones that join, and phones you invite | While the party runs |
| "I am here": your name and phone model, while the app sits on its first screen | Only the party hosts that answered your phone's search (at most 8), so a host can invite you. Not broadcast. | Not kept |
| What the party plays: the queue, song titles and links, who added what, votes, reactions, requests to sing, playback timing and volume, when a song ended on your phone, the timing learned for each phone model, and the song's beat (for the dancing characters) | The phones in your party | For the party |
| Whether your phone stepped out: by your tap, by itself during a call, or — in the Google Play version — because the app was not on screen or something covered the video while a YouTube or SoundCloud song played | The phones in your party | For the party |
| Songs a phone shares from its storage | Sent to each phone in the party, so they all play it at the same instant | See "Songs shared in a party" above |
| A network report, every 10 seconds and at once when something changes (at most once a second): Wi-Fi or mobile data, Wi-Fi signal strength, link speed and band, whether the connection is metered, whether this phone shares its connection or streams on its own mobile data, the Wi-Fi network's gateway address (a local address), how fast the phone downloads, whether it is playing, how far it has drifted, and how long its player stalled, went quiet or did not play | The host phone, which passes each phone's link, grade and figures to every phone in the party. The report contains no network name (SSID), no router ID (BSSID) and no location. | In the host's memory for ten minutes at most; summaries in diagnostic logs |
| Results of sync measurements (section 4) | The host phone | The sound curves are discarded after use. The timings learned are kept in sync memory and logs. |
| A karaoke singer's voice (section 4) | The phones in the party, live | Not stored |
| A block (section 6) | When the host blocks a phone, the host's phone refuses it; when you block a phone, nobody is told | For the party |
The host of a party controls what plays and when, on every phone in it, for as long as you stay. Leave the party to end that. On Android 8.1 and older, the first screen shows the name of your Wi-Fi network; the app never sends it.
4. The microphone
SynkEngine asks for the microphone, together with notifications, when you first open it, after explaining why. If you said no, it asks again when you create or join a party. You can keep saying no: parties still work, and you can line the phones up by ear. You can withdraw the permission at any time in Android's settings.
Syncing the phones
During a party, while "keep in sync" is on (the default), each phone listens to the music for a few seconds at a time to measure how far apart the phones are. This can happen while the screen is off. The sound stays in the phone's memory: the phone reduces it to a loudness curve (one number every 5 milliseconds) or to the moments it heard a test beep, sends only those numbers to the host phone, and throws the sound away. Nothing is recorded or saved.
Finding the beat
On the host phone, while "keep in sync" is on and a song from YouTube or SoundCloud plays with the screen on and another phone in the party, the app listens for 10 seconds at a time, at most three times a song, to find the beat for the dancing characters. Only the beat's timing is kept, and it is sent to the party's phones.
Karaoke
When you sing, your phone sends your voice live over the local network to the other phones in the party, which play it straight away. The app does not record, store or upload it. The people in the room can hear you, as at any karaoke night, and could record you with their own devices.
The microphone test
"Test the mic" records 3 seconds, plays them back on the same phone and keeps nothing. While it is open, it shows a live level meter.
5. What goes to other services on the internet
Your phone contacts these services itself, as described below. They receive your phone's internet address and, as with any web request, its model and Android version, and they handle what they receive under their own policies. We receive none of it.
YouTube (Google)
SynkEngine uses YouTube API Services. By using its YouTube features you agree to the YouTube Terms of Service, and Google's use of the data is covered by the Google Privacy Policy.
- The player. YouTube videos play in YouTube's own embedded player, on every phone. When the app opens outside a party, it plays a short welcome video from our YouTube channel. The player connects to YouTube, which collects data about the playback and may show ads and set or read cookies in the app's player. Those ads and cookies are YouTube's; SynkEngine shows no ads of its own. In the Google Play version, YouTube plays only while the app is on screen and the video can be seen.
- A video that is added. When a YouTube link is added to a party, the app asks YouTube's public oEmbed service for its title and whether it can play in an app, and loads its thumbnail picture (the thumbnails of the songs in your lists too).
- Finding songs — the Google Play version. "Search on YouTube" opens the YouTube app or your browser with your words; you choose the song there and share it to SynkEngine, or paste its link. The app itself searches nothing, browses nothing and reads nothing back from YouTube. "Keep the music going" (on by default) picks the next song from this phone's own saved and recently played songs, and asks YouTube's oEmbed service whether each song it considers can still play in an app — nothing else is sent.
- Finding songs — the version from synkengine.com. When you search in the app, your search words go to YouTube. That version also asks YouTube by itself: in a party, each phone loads a "Recommended" shelf, and the host looks songs up by their title to find a karaoke version, to replace a video that will not play, or to find a missing title; "Keep the music going" chooses a song like the last one by asking YouTube. If you open YouTube's or SoundCloud's pages inside that version, or sign in to your Google account there, you are dealing with Google or SoundCloud directly. We never see your password or your account.
SoundCloud
SoundCloud tracks play in SoundCloud's own player, and the app asks SoundCloud's oEmbed service for a track's title. SoundCloud's Privacy Policy applies.
Spotify
Nothing plays from Spotify, and no Spotify account is used. In the version from synkengine.com, a pasted Spotify link makes the app ask Spotify for the song's title and read the song's Spotify page for its artist, then look for the same song on YouTube (Spotify's Privacy Policy applies). The Google Play version sends nothing to Spotify: it asks you to find the song on YouTube.
Lyrics (LRCLIB)
While karaoke is on, the host phone sends each song's title and artist (for a song from a phone, its file name) and its length to LRCLIB, a free lyrics service, to find the words, whether or not the lyrics are shown.
Internet check (Google)
When Android cannot tell whether the Wi-Fi reaches the internet (for example on a hotspot with no data), the app checks by asking Google's standard address for this, connectivitycheck.gstatic.com, at most once every 20 seconds while that lasts. The request carries no personal data.
Your own mobile data
If you turn on "Stream on my own mobile data" and the party's Wi-Fi has no internet or is metered, the app sends its internet traffic (YouTube, SoundCloud, lyrics and the rest) over your phone's mobile data, while the party itself stays on the Wi-Fi. Your mobile operator's charges apply.
Links you open
This page, YouTube's terms, Google's privacy policy and our social media pages open in your browser or in their own apps, under their own policies. In the version from synkengine.com, so do our website and its payment page.
6. Rules, blocking and reporting
Before anything is shared, the app asks you to accept its terms of use, which say what may not be shared in a party (names, party names, songs, shared files, reactions and the karaoke voice). In a party's list of phones, tap a phone:
- 🚫 Block hides that phone's name, reactions and karaoke voice on your phone. If you host the party, it also removes that phone and refuses it if it tries to come back. A block lasts for the party.
- ⚑ Report opens your email app with a message to us, which you write and send yourself. It names the phone you report (its display name, phone model and app ID), the party's name, your display name, the time and the app version. Nothing is sent unless you send it.
7. Licences, and what reaches us
Joining a party is free. Hosting is free for 40 minutes; after that, hosting needs a licence. The Google Play version sells nothing and shows no prices or payment links: you type in a licence key. In the version from synkengine.com, the app can open PayPal's page, where payment happens under PayPal's terms and privacy policy; to make a key for your phone, we need the Phone ID that you send us with your payment, and we keep the purchase record for as long as accounting rules require. The app itself never sends your Phone ID or any payment detail.
Otherwise, only what you choose to send reaches us: an email, a report (section 6), a message, or the app's logs when you share them and pick an app to send them with. We use them to answer you, to act on reports and to fix problems, and we delete them when they are no longer needed.
8. Permissions the app asks for
| Permission | Why |
|---|---|
| Microphone | Syncing the phones, karaoke, the mic test and finding the beat (section 4). Asked when the app first opens, after an explanation. |
| Notifications | The party notification, with its controls, while a party runs. Asked when the app first opens. |
| Foreground service: media playback and microphone | To keep the party in step, songs from phones playing, and the karaoke microphone working, while the screen is off or you are in another app. (YouTube and SoundCloud play only on screen in the Google Play version.) |
| Internet, network state, Wi-Fi state | To find and join parties, stream YouTube and SoundCloud, and measure the Wi-Fi link (section 3). |
| Change network state | For "Stream on my own mobile data" (section 5). |
| Wi-Fi multicast | To receive other phones' searches for parties, which are broadcast on the network. |
| Wake lock | To keep time while the screen is off. |
| Change audio settings | To give each phone its own part of the sound, with an equaliser on the phone's output. |
The app does not ask for your location, contacts, camera, phone, text messages, photos or storage. Songs from your phone are chosen in Android's own file picker, which gives the app only the songs you pick.
9. Security
Party traffic on the local network is not encrypted, and a party has no password: while you are in one, the app accepts connections from other devices on the same network. Anyone on that network could, with the right tools, see names, song titles and network reports, hear a karaoke voice, and copy songs shared in the party. Host parties on a network you trust, such as your home Wi-Fi or your own hotspot. Licence keys are checked on the phone.
10. Children
SynkEngine is made for adults (the terms of use ask you to be 18 or older) and is not directed at children. We do not knowingly receive personal data from children; the app sends us nothing. If you believe a child has sent us something, write to us and we will delete it.
11. Your rights
Under the Data Protection Act 2017 of Mauritius, and the GDPR where it applies, you can ask what personal data we hold about you, and have it corrected or deleted. Because the app keeps everything on your phone, you can do most of this yourself (section 2). For anything you sent us, write to kavish.m@hotmail.com; we answer within 30 days. You can also complain to the Data Protection Office of Mauritius, or to the data protection authority where you live.
12. Changes
When this policy changes, we update the date at the top of this page.