Privacy policy
Last updated 15 November 2026
The short version
- You can use Theo without an account. Then your progress stays on your phone.
- If you make an account, we keep your email or Apple or Google sign-in, your age band and your progress, so you can back it up and use it on another phone.
- We never show ads, sell your data or track you across other apps and websites.
- Anonymous usage stats are never linked to you, and you can turn them off in Profile.
- You can see or delete your data at any time from the app.
Who we are
Theo is made by Callum Simpson, a sole trader in the United Kingdom, who is the data controller for your information. Contact: callumjohnsimpson@gmail.com.
If you don't make an account
Your lessons, answers, streak and medals are stored only on your phone. We don't receive them.
Unless you turn it off, the app sends anonymous usage stats: which screens are opened, in what order and for how long, with the app version and whether it's iPhone or Android. Each app launch gets a new random number, so these stats can't be linked to you or to each other across launches. We use them to find screens that confuse people. We delete them after 180 days. Turn them off in Profile with "Share anonymous usage stats".
If you make an account
| What | Why |
|---|---|
| Your email address, or the ID Apple or Google gives us when you sign in with them | To sign you in and send sign-in codes |
| Your age band (13 to 15, 16 to 17, or 18 and over), never your date of birth | To keep under-13s out and set safe defaults |
| Your progress: answers, lessons, streak, medals and achievements | To back it up and sync it between your phones |
| Basic device details: iPhone or Android, app version, time zone | To make sync work and fix bugs |
| Whether you have Full Access | To unlock what you paid for on every phone. We never see your card details. |
| Messages you send to support | To answer you |
The legal basis is that we need this to provide the service you asked for (contract), and our legitimate interest in keeping Theo secure and working well.
What we don't do
- No ads and no advertising trackers.
- No selling or sharing your data for marketing.
- No location data.
- No public profiles, chat or messages between users.
- No profiling to decide what you see, apart from Theo choosing which questions you need to practise.
Who helps us run Theo
These companies process data for us, only on our instructions:
| Company | What for | Where |
|---|---|---|
| Neon | Database | London, UK |
| Render | Servers that run the app's back end and this website | Frankfurt, Germany |
| Resend | Sending sign-in codes and support replies by email | United States |
| RevenueCat | Checking your purchase with Apple or Google | United States |
Where data goes outside the UK, it's protected by UK adequacy rules or the UK's approved contract terms. Apple and Google handle payments and their own sign-in under their own privacy policies.
How long we keep it
- Your account and progress: until you delete your account. After that, everything is permanently removed within 30 days.
- Sign-in codes: deleted a day after they expire.
- Anonymous usage stats: 180 days.
Your rights
You can ask to see, correct, download or delete your data, or object to how we use it. You can delete your account yourself in Profile. For anything else, email callumjohnsimpson@gmail.com and we'll reply within a month.
If you're unhappy with how we've handled your data, you can complain to the Information Commissioner's Office at ico.org.uk.
Under 13s
You need to be 13 or over to make an account. Anyone can use Theo without one.
Changes
If we change this policy in a way that matters, we'll tell you in the app before it applies.