Privacy

Last updated 25 September 2026.

What stays on your device

• Your current and longest streak.
• Which days you have completed, and your score on each.
• Your per-decade accuracy, used for “you’re strongest in the 80s”.

All of it lives in the app’s own storage on your iPhone. Deleting the app deletes it. There is no copy anywhere else.

The questions

The whole question bank ships inside the app. Playing the Daily Rewind requires no network connection, and the only thing it sends to us is the finish count described below, which says nothing about how you played. Question updates arrive as an ordinary app update or a file download; neither carries anything about you.

Advertising

Decadia shows at most one ad per session, after your results, and never during a round. Ads are served by Google AdMob, which collects data to deliver and measure them. Google’s handling of that data is described in its own privacy policy.

• If you allow tracking when iOS asks, Google may use your device’s advertising identifier to personalise ads.
• If you decline, or ignore the prompt, Decadia requests non-personalised ads instead. Declining costs you nothing: the Daily Rewind is identical either way.
• In regions where consent is required, Google’s consent form appears before any ad is requested.
• The consent check. After you finish a game, the app asks Google’s consent service which privacy rules apply where you are. Every player’s app does this, Premium included; for a Premium player it happens at most once each time Decadia starts, shows nothing and requests no ad. Google’s service receives what it needs to answer, which its own declaration to Apple lists as approximate location, performance data and product interaction, not linked to you and used only to make the service work. Decadia uses the answer for ads and for the usage-statistics switch described below.

We require any third party that handles data from the app to protect it to at least the standard described here. Google, Sentry and Cloudflare (which hosts decadia.app) are the only three.

Crash reports

If Decadia crashes, freezes or hits an internal error — for example, an ad that fails to load or to appear — or iOS stops it for using too much memory, or flags it for using too much processor time or writing too much to storage, it sends a diagnostic report to Sentry so the fault can be found and fixed. Sentry’s handling of that data is described in its own privacy policy.

A report describes the failure and the device, not you:

• What is sent: where in the code the app stopped, the iOS version, the device model, and the app version. Some of these reports come from Apple’s own diagnostics on your device (MetricKit). Where the app was stuck, or used too much processor time or storage, arrives the next time you open it. When iOS stopped the app, how many times it did so that day and the most memory the app used arrive about a day later, and only if it was stopped at all.
• No screenshot and no view hierarchy. The question you were looking at is never photographed — Decadia’s share card is deliberately spoiler-free, and a crash report will not undo that.
• No identifier in the report, and no session replay. Decadia has no accounts, so there is no account to name. The report is stripped of any user, of your device’s name and of the per-install value the reporting tool would otherwise attach, before it is sent. From version 1.0.6 the session record for that launch (below) is marked as crashed, and that record does carry its random ID.
• Nothing about your play. Not your streak, not your score, not which answers you chose.

Crash reporting cannot be switched off separately, because a report is only ever produced when something has gone wrong: the app failed, froze, was stopped, or was flagged by iOS for how much it used. If that matters to you, the honest answer is that the app is telling us it misbehaved.

What the app tells us about use

Until version 1.0.6 Decadia measured nothing about use at all, and so we could not tell whether anyone was playing. From 1.0.6 it measures two things, and only these two.

Session records, via Sentry

Each time you open the app, or return to it after more than 30 seconds away, it sends Sentry a short record of that session: when it started and ended, the app version, and whether it ended normally, crashed or hit an internal error. The record carries a random ID that Sentry’s software created on your device the first time the app ran, so that several launches on one install count as one player rather than several.

• The ID is a random number and nothing more. It is not linked to your Apple Account, your advertising identifier or your Game Center identity, and we do not link it to anything else.
• Deleting the app deletes the ID. A new install starts with a new one.
• Sentry is set not to store your IP address or any location derived from it.
• The record contains nothing about your play: not your streak, your scores, your answers or which questions you saw.

We use these records for two numbers: how many people use Decadia each day, and what share of sessions on each version end in a crash.

Switching them off. The Share usage statistics switch on Decadia’s home screen turns session records off, or back on. A change applies from the next time Decadia starts, not immediately, and the switch says so. Your own choice always wins over the defaults below.

Where the law requires your consent for this — the European Economic Area, the United Kingdom, Switzerland, Jersey, Guernsey, the Isle of Man and Gibraltar — the switch is off by default. Decadia can tell where you are in only two ways: the region set on your iPhone, and the answer Google’s consent service gives the app, which first arrives after you finish your first game.

• If your iPhone’s region is set to one of these places, the switch is off from the first time you open Decadia.
• If it is not, but Google’s consent service tells the app you are in one of them, the switch turns off then, and session records stop from the next time Decadia starts. Some may have been sent before that.
• Once Google’s service has answered, its answer is the one Decadia goes by. If neither is known, the switch starts off.
• Everywhere else it starts on.

Crash reports are not affected by this switch.

The finish count, via decadia.app

The first time you finish a day’s Daily Rewind on this install, the app sends decadia.app two things: that day’s number (the “15” in “Decadia #15”) and the app version. That is all. It carries no identifier of any kind, so two finishes can never be connected to each other or to you. Playing the same day again, playing a past day from the Archive or playing a Decade Dive adds nothing to the count.

decadia.app is hosted by Cloudflare, which, like any web server, sees the connection’s IP address in order to answer it. We do not store the IP address, or anything else about the connection, with the count. What is kept is one line per finish, “someone finished day 15 on version 1.0.6”, for three months.

It is how we count how many Rewinds are finished each day.

What we still never collect

• Your scores, your answers, your streak or your per-decade stats. A finish tells us only that someone finished day 15, not how well.
• Which questions you saw, how long you spent on them or where you stopped.
• Anything from the Archive or Decade Dives.
• Your name, your email, your Apple Account or your Game Center identity.

The finish count is not affected by the switch and has no switch of its own: it carries no identifier, nothing about it is stored on your device, and a finish can never be connected to you, so there is nothing personal in it to consent to. If that matters to you, email us and we will answer plainly.

A correction. Versions 1.0 to 1.0.2 also send Sentry the session record described above. That was the reporting tool’s default setting, we had not switched it off, and at the time this page said no identifier was ever sent. Versions 1.0.3 to 1.0.5 send no session record. From 1.0.6 it is on again, deliberately this time, and described in full here. The record never contains your streak, your scores or your answers.

The web game

Playing today's Daily Rewind at decadia.app/play works differently from the app, because there is no app storage to keep anything in. Each question and each answer check is a request to decadia.app: the browser asks for today's ten questions, and sends each choice to be checked, one at a time. Finishing sends the same anonymous finish count described above, tagged “web” instead of an app version — nothing else is added.

• The day's result — the score and which questions you got right — stays in that browser's own storage, so a return visit the same day can show it back to you. It is never sent to us, and it holds no identifier.
• The finish count is the same one-per-day, no-identifier count as the app’s: a day number and “web”, nothing else.
• No cookies, no ads, and no analytics beyond that one count.

Game Center

Leaderboards and achievements are provided by Apple’s Game Center. When you finish a Rewind, Decadia submits your score and streak to Apple. Your Game Center identity is never sent to us. The app keeps your player ID on your device only, so that each score and achievement goes to the player who earned it.

On the results of today’s Daily Rewind you can tap SEE HOW YOUR FRIENDS DID. Only then does Apple ask whether Decadia may see your Game Center friends list, and only if you allow it does the app read your friends’ names, player IDs and scores from Game Center. Once you have allowed it, the app reads them again on the results of each later day’s Daily Rewind, to show how your friends did that day — always on your device, only to show them to you. They are never stored, and never sent to us.

Signing in is entirely optional and declining does not limit the game in any way.

Purchases

Decadia Premium is sold through Apple. Payment is handled entirely by Apple and we never see your payment details. The app only learns whether a valid purchase exists.

Children

Decadia is a general-audience trivia game and is not directed at children. We do not knowingly collect information from children.

Your data, and removing it

Everything the app records about your play stays on your device, so there is no account to close. Deleting Decadia removes all of it, including the random ID used by session records. The finish count holds nothing that could be traced back to you, and the session records hold only that random ID, which we cannot connect to you. Sentry keeps session records for 30 days, the retention of Decadia’s Sentry plan; finish counts are kept for three months. Both are then deleted. To reset advertising personalisation, use Settings › Privacy & Security › Tracking on your iPhone. Game Center data is held by Apple and can be managed through your Apple Account.

Changes

If this policy changes in a way that affects what is collected, the date at the top will change and the app will be updated to link to the revised version.

Contact

Questions about privacy: [email protected]