GutMaxx Diary privacy policy
Last updated: 5 November 2026
Who we are. GutMaxx Diary is made by Josh Bates (sole trader) (“we”). We are the controller of the limited personal data described below. Contact us at hello@gutmaxx.co.uk. We don’t have a Data Protection Officer; Josh Bates handles privacy questions.
The short version
- Your diary (foods, ingredients you watch, symptoms, bowel habits, how you feel, notes and photos) is stored only on your phone. We never receive it.
- There’s no account and no sign-up.
- Usage stats are off unless you turn them on. Crash reports are on by default and you can turn them off. Neither includes anything you type or log.
- Barcode scanning happens on your phone. Only the barcode number is sent, to Open Food Facts, to look up the product.
- You can export or delete everything in the app at any time.
- Test versions (closed testing only): test versions of the app don’t send usage stats, crash reports or subscription data, and purchases are simulated. Only barcode lookups go to Open Food Facts.
What stays on your phone. Everything you enter in the diary, and the products you’ve logged from barcode scans. Because the diary includes health information, we ask for your explicit consent before you start, and you can withdraw it in Settings. Withdrawing consent deletes your diary from the phone. Backups are optional, encrypted with a passphrase you choose, and saved to a place you pick. We can’t open them, and we can’t recover a lost passphrase. Meal photos aren’t included in backups or exports. If you save a backup to a cloud folder, that provider stores the encrypted file.
What leaves your phone, and why
| What | Who receives it | Why | When / your choice |
|---|---|---|---|
| The barcode number you scan, your device’s IP address, and the app’s name and version | Open Food Facts, a French non-profit food database. It decides how it uses this, under its own privacy policy (openfoodfacts.org), and keeps its own server logs, including IP addresses | To look up the product you scanned | Only when you scan a barcode. Searching foods in the app never contacts them. The camera image is read on your phone and never sent anywhere |
| Usage counts from a fixed list (for example “a meal was logged by search”, “the subscription screen was viewed”, “a PDF was exported”), plus app version, device type and Android version, linked to a random ID | PostHog, our analytics service | To see which features work and improve the app | Off by default. Nothing is sent unless you turn on “Share usage stats”. Turn it off at any time in Settings > Privacy |
| Crash reports: what went wrong in the app’s own code, app version, device model, Android version and a random ID. No names, contact details or anything you log. Crash reports cover app errors only (native crash reporting and screen recording are off) | Sentry, our crash-reporting service | To find and fix faults | On by default. Turn off in Settings > Privacy |
| Plan prices for your country, and your purchase: your Google account, payment details and order | Google Play. Google Play’s billing software runs in the app; its own privacy policy applies. It sends us order records such as order number, product and date | To show you the prices, take payment and run your subscription | Prices: when the subscription screen is shown (including once at the end of setup). Purchase: only if you start a trial or subscribe |
| Subscription status and purchase details, linked to a random subscription ID, plus app version, device type and store country | RevenueCat (US), our subscription service | To unlock Plus and keep it unlocked | Only from the first time you tap to start a trial, subscribe or Restore purchases, and then each time the app starts so Plus stays unlocked. Just viewing the subscription screen sends RevenueCat nothing (the prices come from Google Play) |
| Your email and message, if you contact us | Us, and our email provider | To answer you | Only if you email us |
| That you came from the app, when you tap “Read more on GutMaxx” | gutmaxx.co.uk, opened in your browser (see the website’s privacy and cookie policy) | To show the guide page | Only when you tap a link |
| Your PDF, CSV or backup file | Whoever or wherever you choose to send or save it | Your choice | Only when you export, share or back up |
Google Play’s billing software runs in the app to show prices and take payments, under Google’s privacy policy.
None of these include anything you type or log in your diary, apart from the barcode number you scan. We don’t sell data, show ads or use advertising IDs.
Legal bases (UK GDPR)
- Your diary (health information): your explicit consent (Articles 6(1)(a) and 9(2)(a)). It’s processed only on your phone.
- Usage stats: your consent (Article 6(1)(a)), given by turning on “Share usage stats”.
- Crash reports: our legitimate interest in finding and fixing faults so the app keeps working (Article 6(1)(f)).
- Barcode lookups: our legitimate interest in giving you the product lookup you asked for (Article 6(1)(f)).
- Subscriptions: to perform our contract with you (Article 6(1)(b)), and to meet tax and accounting law for payment records (Article 6(1)(c)).
- Emails you send us: our legitimate interest in answering you (Article 6(1)(f)), or our legal obligation when you exercise your data rights (Article 6(1)(c)). If you choose to tell us about your health in an email, we use it only to answer you, and you can ask us to delete it.
- Complaints: our legal obligation to handle complaints about how we use personal data (Article 6(1)(c)), the complaints duty in section 164A of the Data Protection Act 2018. If a complaint includes health details, we handle them for reasons of substantial public interest (UK GDPR Article 9(2)(g) and Data Protection Act 2018 Schedule 1 paragraph 6, statutory purposes: the complaints duty in section 164A), and only to deal with the complaint. Please don’t include diary details; if you do, we remove any we don’t need to handle the complaint.
Data sent outside the UK. Usage stats (PostHog) and crash reports (Sentry) may be processed by US-based companies under the UK Extension to the EU-US Data Privacy Framework or the UK International Data Transfer Addendum once those accounts are live; we will update this section with the confirmed hosting region then. Subscription data handled by RevenueCat is stored in the US under the UK Addendum to the EU Standard Contractual Clauses. Open Food Facts is based in France (EU). Google processes Play purchases worldwide under its own policies. Contact us for a copy of the safeguards.
How long we keep things
- Diary: on your phone until you delete it, withdraw consent or uninstall the app.
- Usage stats: deleted automatically after a set period once analytics is live; we will publish the exact months here when the PostHog account is confirmed.
- Crash reports: deleted automatically after a set period once crash reporting is live; we will publish the exact days here when the Sentry organisation is confirmed.
- Subscription records: while your subscription is active, then as required for tax and accounting law.
- Emails to us: for a limited time after your question is closed.
- Complaints: 6 months after closing, then deleted automatically.
- Open Food Facts and Google keep their own logs and records under their own policies.
Your rights. You can see, correct, export and delete your diary in the app. For usage stats, crash reports or subscription data you can ask us for a copy, a correction, deletion or restriction, or to move it to another service. Email hello@gutmaxx.co.uk and quote the IDs shown in Settings > Privacy (tap Copy next to each; the subscription ID appears only if you’ve tapped Subscribe or Restore purchases). We reply within one month.
You can object at any time to processing based on our legitimate interests, including crash reports: turn off “Send crash reports”, or email us.
You can withdraw consent at any time: turn off “Share usage stats”, or withdraw diary consent in Settings > Privacy > Withdraw consent. This doesn’t affect what happened before you withdrew.
Complaints (linked from the app: Settings > Privacy > Make a privacy complaint)
If you have a complaint about how we use your data, use the “Make a privacy complaint” form below, or email hello@gutmaxx.co.uk. The form shows your complaint reference, with the date and time we received it (UK time), on the page straight away. Please save it. We’ll acknowledge emailed complaints within 30 days. We’ll look into your complaint, keep you updated by email and tell you the outcome. Please don’t include details from your diary, like symptoms or foods; we don’t need them. If you’re unhappy with our response, you can also complain to the Information Commission (ICO) at ico.org.uk/make-a-complaint.
We handle complaints because the law requires us to (see “Legal bases”), not on the basis of your consent. We use what you send only to handle your complaint, and keep it for 6 months after closing (see “How long we keep things”).
Automated decisions. We don’t make any decisions about you by automated means. Patterns are simple counts of your own entries, worked out on your phone.
Where your data comes from. From you and your phone, and, if you subscribe, order records from Google Play.
Do you have to give it? No. Without your consent to store health information, the diary can’t be used. Usage stats are optional. A subscription needs a Google Play purchase.
Things stored on your phone (PECR). If you turn on usage stats, PostHog stores a random ID on your phone and reads basic device details; this only happens with your consent. Sentry stores a random ID on your phone so crash reports can be grouped; this is needed to find faults. Turning off crash reports stops anything being sent. Once you’ve tapped to start a trial, subscribe or Restore purchases, RevenueCat stores a random ID and your subscription status on your phone, and the app checks it each time it starts so Plus stays unlocked. Viewing the subscription screen only asks Google Play for prices. Barcode scanning uses open-source software on your phone and stores nothing for anyone else. We use no advertising ID and no ad trackers.
Security. Data sent from the app is encrypted in transit. Backups are encrypted with your passphrase. You can lock the app with your fingerprint or PIN.
Age. GutMaxx Diary is for adults (18+). If you’re under 18, please don’t use it.
Not medical advice. GutMaxx Diary is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. Always talk to your GP or a qualified healthcare professional about your symptoms.
Data sources (same text as the app’s Settings > About > Data sources)
- Fibre values are derived from McCance and Widdowson’s The Composition of Foods Integrated Dataset 2021 (Public Health England), adapted and rounded by GutMaxx Diary. © Crown copyright 2021. Contains public sector information licensed under the Open Government Licence v3.0. Not endorsed by PHE, OHID, the NHS or the UK Government.
- Contains information from Open Food Facts, which is made available here under the Open Database License (ODbL). Individual contents are available under the Database Contents License. Product data comes from labels added by volunteers and may contain errors.
- Barcode scanning uses ZXing, licensed under the Apache License, Version 2.0.
Changes. We’ll update this page and the date above, and tell you in the app if anything important changes.