Last updated: 9 November 2026

CrateCheck is a browser extension that helps DJs find where to buy the tracks
they discover while browsing streaming sites, and flags tracks they already own.
This policy explains exactly what the extension does and does not do with your
information. In short: CrateCheck has no servers of its own and sends us only two
things: anonymous, opt-out usage counts, which never include the music you search or
own, and, once you've agreed, crash reports when something breaks. A crash report
keeps the error message with web addresses removed, so it could rarely include a
track name.

• We do not ask for or set out to collect personal information such as your name or
  email address.
• We have no backend. There is no CrateCheck server that receives your data.
• We collect anonymous, opt-out usage analytics — counts and activity,
  never the names of tracks you search or anything from your library.
• We do not collect your location.
• Once you've agreed, we collect crash reports when something breaks. An error
  message could rarely include a track name, and people at CrateCheck may read
  these reports to fix the problem.
• We run no advertising and no fingerprinting, and we never sell your data. We
  share it only with PostHog, which processes it for us.
• Everything else happens on your computer, including reading your Rekordbox
  and Serato libraries, which the optional CrateCheck Desktop app reads on your Mac
  or Windows PC.

To do its job, CrateCheck does three things in your browser:

1. Reads track details on the page you're viewing. On Spotify and SoundCloud,
   CrateCheck reads the title, artist, and duration of the tracks shown so it can
   add its button and know what to search for. When you click the button, the
   title and artist go to the music stores as your search (see 2 below). This
   information is not sent to us, except that a crash report's error message
   could rarely include a track name (see "Crash reports" below).
2. Searches the music stores you buy from. When you click CrateCheck's button,
   the extension queries the supported stores — currently Beatport, Qobuz,
   Bandcamp, iTunes/Apple Music, SoundCloud, Traxsource, and Amazon Music — to
   find that track and show matching results.
   These requests go directly from your browser to those stores. Where you are
   logged in to a store, the request uses your existing browser session — exactly
   as if you searched that store yourself — so results match what you would
   normally see. CrateCheck does not collect, read, or transmit your store
   credentials, cookies, or session tokens; it cannot see them and never sends
   them anywhere. The only thing sent to a store is the search text (track title
   and artist).
3. Optionally checks tracks against your Rekordbox and Serato libraries (see
   below), so you don't buy music you already own.

The ownership feature is opt-in and runs entirely on your device. It works
through CrateCheck Desktop, an optional, small app for your Mac or Windows PC that
reads your Rekordbox and Serato libraries so the extension doesn't have to. You install it
yourself, and it only runs while the extension is talking to it. Your library stays
on your computer. The one rare exception is a track name inside a crash report's
error message (see "Crash reports" below).

• What it reads. Your Rekordbox master.db and your Serato DJ 4 or 5 library's
  master.sqlite (or root.sqlite beside it, if there's no master.sqlite),
  read-only. Serato's master.sqlite covers your tracks on every drive, so CrateCheck
  Desktop doesn't need to open your other drives. By default it looks in each app's
  usual place (~/Library/Pioneer/rekordbox/master.db and
  ~/Library/Application Support/Serato/Library/master.sqlite on a Mac,
  %APPDATA%\Pioneer\rekordbox\master.db and
  %LOCALAPPDATA%\Serato\Library\master.sqlite on Windows); you can point it at a
  different file, or turn either one off, from the extension's Library settings. It
  never changes either database and never copies them anywhere.
• What it keeps. Its own files live in ~/Library/Application Support/CrateCheck
  on a Mac and %LOCALAPPDATA%\CrateCheck on Windows: a word index of your tracks
  (catalog.db) so checks are fast, which libraries to read and where they are
  (helper.json), and a copy of the app itself (bin/). It also caches the key
  Rekordbox uses to lock its own database (key-cache.json), so it doesn't have to
  work it out every time. That's Rekordbox's key, not a password of yours. It
  writes no logs. On Windows, the installer also puts the app in
  %LOCALAPPDATA%\Programs\CrateCheck Desktop, and your browsers find it through
  registry entries under your user account.
• What leaves your machine. Nothing. Desktop has no network code at all. It
  talks only to the CrateCheck extension in your browser, over a local connection,
  and only CrateCheck can start it.
• What the extension sends it. The words from the title and artist of the track
  you're looking at. Desktop answers with the tracks in your library that could
  match, which the extension checks and shows you in the side panel. All of this
  stays between the extension and Desktop, on your computer; it isn't sent to us,
  apart from that same rare crash report case.
• What the extension keeps. No copy of your library. The extension only stores
  that Desktop is connected, where your libraries are, and how many tracks each has.
• Removing it. On a Mac, run cratecheck uninstall in Terminal. On Windows, find
  CrateCheck Desktop in Settings › Apps and choose Uninstall. That removes
  the browser registrations, the app, and everything in its folder above, including
  the index. One exception on Windows: if a browser has Desktop open at that moment,
  the index and the cached key stay until the browser closes Desktop (closing the
  browser does it), and then they go too. A copy of the app itself stays in that
  folder until you next install or uninstall, or delete it yourself. Your Rekordbox
  and Serato libraries are untouched.
  Removing the extension alone doesn't remove Desktop.

When a track is in your library, CrateCheck marks its button on Spotify or
SoundCloud with a check. Like any button on a web page, that mark is visible to the
page, so the site's own scripts could in principle tell that CrateCheck is installed
and which tracks carry the check. CrateCheck never tells those sites anything
itself; this is simply how showing a badge on a page works. If you'd rather not,
disconnect your library in the extension's settings and the buttons go back to
plain.


CrateCheck uses your browser's local extension storage, all of which stays on your
device and is never synced or transmitted:

• A short-lived note of the track you just clicked, so the side panel knows what
  to display when it opens.
• A temporary cache of store search results (with a short expiry) so the same
  search isn't repeated unnecessarily.
• If you use CrateCheck Desktop, a note that it is connected, your libraries'
  locations, and their track counts. No copy of your library.
• Your choices about usage counts and crash reports.

On Firefox, the search cache and your libraries' locations are kept only until you
close the browser, because of how Firefox's storage works.


CrateCheck includes anonymous usage analytics to help us understand whether
features work and get used, so we can improve the extension. It is on by default
and you can turn it off at any time from the extension's settings.

• What it records: anonymous, aggregate usage events only. For example: that a
  search was run, how many stores returned a result, that a result link was
  clicked, and which days the extension was active. When a store search fails, we
  also record which store and what kind of failure it was (for example a bot check,
  or a page that didn't parse), never what you searched for. If you connect
  CrateCheck Desktop, that you did and how many tracks your libraries have. Each event also carries a random
  ID that isn't tied to you (kept in the extension's own storage) and your browser
  and operating system versions, language, time zone and screen size. PostHog receives your IP address with each request, but CrateCheck tells it not to work out a location from it, and it doesn't keep the IP address.
• What it never records: the names of tracks you search, your Rekordbox or
  Serato library or any of its contents, file paths, anything CrateCheck Desktop reads, or
  personal information such as your name or email address. Nothing about the music you look for or own is included
  in these usage events.
• Who processes it: these events are processed by PostHog, on its US
  infrastructure, acting as our data processor. We use the data only to operate and
  improve CrateCheck, and we do not sell it.
• Turning it off: untick "Share usage and crash reports to help improve
  CrateCheck" in the extension settings. When it is off, no usage events are sent.
  On Firefox you can also turn off "technical and interaction data" when you install
  CrateCheck, or later under Permissions and data in about:addons. Either way
  nothing is sent, and the setting above shows as off until you turn it back on.

If a Spotify or SoundCloud update stopped CrateCheck's buttons from appearing, we'd
have no way to find out, so the extension checks for it. This is one of the usage
events above, and the same setting turns it off.

• What it checks, on your device: on a page that should list tracks, it looks for
  signs that tracks are there (links to tracks on Spotify, waveforms on SoundCloud)
  and whether they got their buttons. Working pages send nothing.
• What it sends: when the buttons are missing, or reading a track failed with an
  error, one report, at most one per site per day, plus one each for Spotify's Now
  Playing view and player bar. It holds only the site, the kind of
  page (for example an album), the step that failed, the extension version and the
  browser (Chrome or Firefox).
• What it leaves out: track names and page addresses. Each report has its own new
  random ID, not the one above, so reports can't be linked to each other or to your
  other events. It also carries no operating system, language, time zone or screen size.

If CrateCheck Desktop meets a Serato version it can't read yet, or one too old to
read, we'd have no way to know which versions to support next, so the extension
tells us. This is one of the usage events above, and the same setting turns it off.

• When it's sent: only when CrateCheck Desktop can't read a library because its
  app version is too new or too old, at most once a day per version.
• What it sends: the app (Serato), whether it was too new or too old, the
  library's format number when there is one, your operating system (Mac or Windows),
  the CrateCheck Desktop and extension versions and the browser.
• What it leaves out: file paths, track names and anything else from your
  library. Each report has its own new random ID, not the one above, so reports can't
  be linked to each other or to your other events.

When the side panel (on Firefox, the sidebar or its floating window) or welcome page hits an error it can't handle, CrateCheck can
send a crash report so we can find and fix the problem. The side panel tells you
about this once, with "Got it" and "Turn off in settings". No crash report is sent until you
press "Got it" or switch the setting above back on.

• What a report contains: the error's type and message, with web addresses
  removed, and where in CrateCheck's own code it happened. It also carries the same
  details as a usage event: the random ID, your browser and operating system
  versions, language, time zone and screen size.
• What a message could include: the message is otherwise sent as written. Errors
  sometimes quote what the code was working on, so a message could rarely include a
  track name, or other text from what CrateCheck was handling at the time. We don't
  look for this, and we don't use it for anything except fixing the problem.
• Who sees them: crash reports are processed by PostHog, on its US
  infrastructure, acting as our data processor, and people at CrateCheck may read
  them to fix the problem. We do not sell them.
• Turning them off: untick "Share usage and crash reports to help improve
  CrateCheck" in the extension settings ("Turn off in settings" on the notice takes
  you there). This one switch covers usage events and crash reports, and takes
  effect straight away. Firefox's own setting, above, covers them too.

Firefox lists the data an add-on can collect when you install it. For CrateCheck it
names technical and interaction data (usage counts and crash reports), which you can
turn off there, plus website content (the track name a click sends to the music
stores, and the rare track name in a crash report's error message). Firefox doesn't
let website content be turned off on its own. Crash reports stop while the setting
above is off; store searches still go to the stores when you click, since that's what
CrateCheck does.


When CrateCheck searches a store or links you to a purchase page, you are
interacting with that third party's website (Spotify, SoundCloud, Beatport, Qobuz,
Bandcamp, Apple, Amazon, Traxsource, etc.). Those sites have their own privacy
policies, which govern any data they collect. CrateCheck has no control over and
no access to what those sites do.


We do not sell or rent any user data. The only data we collect is the anonymous,
opt-out usage analytics and the crash reports described above, used solely to
operate and improve CrateCheck. We share it only with PostHog, which processes it
for us.


On the Chrome Web Store, CrateCheck's use of user data complies with the
Chrome Web Store User Data Policy,
including the Limited Use requirements.


CrateCheck is a tool for music buyers and is not directed at children.


If this policy changes, we will update the "Last updated" date above and post the
revised policy at the same URL.


Questions about this policy or the extension:

• Email: contact@cratecheck.app