Privacy Policy

Last updated 12 October 2026

Craterline is a free game, in your browser and as an app for iPhone and Android. You never need an account to play; signing in is optional. We collect as little as we can and still run a fair match, we never sell any of it, and this page says exactly what that little is.

Who we are

Craterline (“we”, “us”) is an independently made browser game. We decide what happens to the information described here. For anything about your data, email hello@craterline.net.

What we collect, and why

When you play

• Your call sign. The name you type before a match. Your opponent sees it, the server holds it in memory for the match, and it is written to our server logs when a match starts or an invite code or challenge link is used. It is not linked to an email address or an account. If you would rather not use your real name, don’t.
• Connection data. Like any website, our server sees your IP address and your browser’s user agent when you connect. We use the address, in memory only, to limit how many connections and requests one address can make — that is how the game stays up for everyone. Our hosting provider may also keep standard web server logs, which include IP addresses, for security and operations.
• The match itself. Your aim, your shots and the result pass through the server, which runs the match. When a match ends we log its outcome and length, without call signs. There are no leaderboards, no stats and no match history.

If you sign in

Signing in is optional, and guest play works exactly the same without it. Sign-in is handled by Auth0 (Okta), with the account you choose there — for example Google, Apple or Microsoft. We ask Auth0 for nothing but a user id: not your name, not your email address, not your picture. Auth0 keeps your sign-in under Okta’s privacy policy; what Auth0 receives from Google, Apple or Microsoft is between you and them.

In our database we store, for each account, that Auth0 user id, an id we make up for the account, the call sign you choose, and when the account was made. Your browser holds one cookie, craterline.account, that keeps you signed in; it holds only our account id, scrambled so that only our server can read it, and no script on the page can read it at all. You can have your account deleted at any time by emailing hello@craterline.net. Deleting it removes it from our database and deletes your user at Auth0 too.

When you make a challenge link

A challenge link is yours to keep and share. To make it work between visits we store, in our database, the link’s id, a one-way scrambled copy (a hash) of the secret that proves your browser owns it, and when it was made and expires — no call sign and nothing else about you. The link expires, and its record is deleted automatically, if you don’t come back to the game for three months. Anyone you give the link to can use it to start a match with you while you have the game open.

When you send feedback

The in-game “Send feedback” form sends us what you write, the category you pick, which screen you were on, the game version and, if you were in a match, that match’s id. We add an anonymous reference that stops meaning anything once you disconnect — it cannot be used to recognise you later. Reports are written to our server logs, kept in our database for up to twelve months and then deleted automatically, and may be copied into our issue tracker on GitHub so that they get fixed. There is no reply address, so please leave personal details out.

Stored on your device

The game keeps a few small items in your browser’s local storage so it works: your last call sign, a random guest id, a short-lived token that puts you back into your match if you refresh or lose connection, your challenge link and the secret that proves it is yours, whether you have dismissed the “turn your phone sideways” hint, and your cookie choice. None of these is used for tracking. The Cookie Policy lists every one.

In the iPhone and Android apps

The app is the same game. When you play online — a duel against another player — it talks to the same server, and everything under “When you play” above applies unchanged. Practice against the computer runs entirely on your phone and sends nothing to anyone.

The app keeps the same few items on your phone that the website keeps in your browser, so it works: your last call sign, a random guest id, whether you have dismissed the hint to turn your phone sideways, and, while you are in an online match, that match’s id, the token that puts you back into it and when that token stops being worth keeping. If you make a challenge link, it also keeps the link and the secret that proves the link is yours. The token and that secret are kept in your phone’s secure storage (the iOS Keychain or the Android Keystore), never alongside the rest. Uninstalling normally removes the app’s data, but iOS may keep Keychain items after uninstall, so those credentials can remain if you reinstall the app.

The app has no analytics, no advertising and no cookies, contacts no server other than ours, and asks for no permissions beyond network access and vibration, which it uses for haptic feedback. Apple and Google handle downloading and updating the app under their own privacy policies.

Analytics — only if you say yes

If you choose Allow analytics on the cookie banner, the game loads two tools. If you choose No thanks, or never answer, neither is loaded at all.

• Google Analytics (Google) records how you arrived — the referring site and any campaign tags in the link — along with your device, browser, rough location from your IP address, the screens you visit, and game events such as joining the queue or starting and finishing a match.
• Microsoft Clarity (Microsoft) records how you use the page — clicks, taps, scrolling and what is on screen — so we can see where the game is confusing. Call signs are masked out of these recordings, and so is anything typed into a text box.

Neither tool is ever sent your call sign, your rejoin token or a match id, and advertising features are switched off in both. They set cookies, listed in the Cookie Policy, where you can also change your answer at any time. Google and Microsoft handle this data under their own policies: how Google uses data from sites that use its services and the Microsoft Privacy Statement.

Error reports

When the game server hits an unexpected error, it may send a technical report to Sentry, an error-tracking service: what went wrong and where in our code. Reports are deliberately stripped of request details — no addresses, headers, cookies, tokens or call signs.

Advertising

The ad spaces in Craterline are placeholders today: no ad network is loaded and no advertising cookie is set. We plan to show ads from Google AdSense. Before that happens we will update this policy and the cookie banner, and ask for your consent where the law requires it.

Once ads run, third-party vendors, including Google, use cookies to serve ads based on your prior visits to this website or other websites. Google’s use of advertising cookies enables it and its partners to serve ads to you based on your visits to this site and/or other sites on the internet. You can opt out of personalised advertising in Google’s Ads Settings, and out of some other vendors’ use of cookies for personalised advertising at aboutads.info.

How we use it

• To run the matches you ask to play, and to put you back in one after a dropped connection.
• To keep the game secure and fair, and to stop abuse — see the Terms of Service.
• To find and fix bugs, and to decide what to improve next.

We do not sell personal information, share it for cross-site advertising, build profiles of players, or make automated decisions about you that have legal or similar effects.

Legal basis (EEA and UK)

• Running the game, keeping it secure, handling feedback and error reports: our legitimate interest in providing a working, fair game you have chosen to play.
• Analytics: your consent, which you can withdraw at any time.
• Anything we are required to keep or disclose: our legal obligations.

Who we share it with

Only service providers that process it on our behalf, and only what each one needs: Microsoft Azure (hosting), MongoDB Atlas (our database, for feedback, challenge links and accounts), Auth0 by Okta (sign-in, only if you sign in), Sentry (error reports), GitHub (our issue tracker) and, only with your consent, Google and Microsoft for analytics. We will also disclose information if the law requires it. Some of these providers process data outside your country, including in the United States; where they do, we rely on the safeguards they provide, such as the EU Standard Contractual Clauses or the EU–US Data Privacy Framework.

How long we keep it

• Call signs and match state: in memory until the match ends, and at most an hour after.
• Server logs: for a limited period, and no longer than we need them for security and troubleshooting.
• Feedback: up to twelve months, then deleted automatically.
• Challenge links: until three months after you last came back to the game, then deleted automatically.
• Accounts: until you delete yours, which also deletes your user at Auth0. The sign-in cookie lapses after thirty days without a visit.
• Analytics: under Google’s and Microsoft’s own retention settings, for no longer than fourteen months.
• Browser items remain until you clear site data. App data is normally removed on uninstall, but iOS may keep Keychain credentials, such as the rejoin token and challenge-link secret, across uninstall and reinstall. The rejoin token is dropped once its match is over, and the cookie banner asks again after six months.

Your rights

Depending on where you live, you may have the right to see the personal information we hold about you, correct it, delete it, restrict or object to how we use it, receive a copy, and withdraw consent you have given. You can also complain to your data protection authority. To use any of these rights, email hello@craterline.net.

If you have an account, email us to have it deleted. Everything else we hold is not tied to an account, so we usually cannot tell which data is yours. To find feedback you sent, for example, tell us roughly when you sent it and what it said. California residents: we do not sell or share personal information as the CCPA defines those terms.

Children

Craterline is suitable for general audiences, but it is not directed at children under 13 and we do not knowingly collect personal information from them. There is no chat and no profile, and the only thing another player can send you is a call sign. If you think a child has sent us personal information — in a feedback report, say — contact us and we will delete it. In the EEA and UK, players under 16 should ask a parent before allowing analytics.

Changes to this policy

When this policy changes, the date at the top changes with it. If we start collecting something new that needs your consent — ads, for example — the cookie banner will ask you again rather than assume your earlier answer covers it.

Contact

Questions, requests or complaints about privacy: hello@craterline.net.