Mực Thước app icon

Privacy Policy — Mực Thước

Luban ruler (墨尺) · Official Privacy Documentation

📅Effective Date: October 10, 2026
🔄Last Updated: October 10, 2026
📦 Application ID / Package: dev.techfusion.luban
🏢Developer / Publisher: Techfusion Ltd (support@techfusion.dev)

Quick Reference Summary

AttributeDetails
App PurposeA Luban ruler (thước Lỗ Ban) for checking the sizes of doors, furniture and altars, and saving them in projects.
User AccountsNone. No sign-in, registration or cloud account.
Our ServersNone. The app does not send your projects, sizes, photos or settings to us.
Data on Your DeviceProjects, saved items, optional photos, settings and purchase status, kept in the app's private storage.
PhotosOptional. Taken with your camera app or chosen in the system photo picker. The app keeps a resized copy without the original metadata, such as location. No camera or storage permission.
AdvertisingFree version: one Google AdMob banner on the project list. Consent through Google UMP where the law requires it. No ads after either purchase.
PurchasesGoogle Play Billing. Google handles payment; we never see your card details.
AudienceGeneral audience. Not directed at children under 13.
DeletionDelete items or projects in the app, or uninstall the app to erase everything on the device.
Contactsupport@techfusion.dev

1. Introduction

This Privacy Policy explains how Mực Thước (墨尺, "the App"), published by Techfusion Ltd ("we", "us"), handles information. The App is a Luban ruler: it checks the sizes of doors, furniture and altars against the traditional ruler sections and lets you save them in projects.

In short: your data stays on your device. The App has no accounts and we run no server for it. The only third parties involved are Google AdMob (ads in the free version) and Google Play (purchases).

2. No Accounts, No Server

  • The App has no sign-up or sign-in.
  • We do not operate a server for the App. It never sends your projects, sizes, photos or settings to us or to anyone else.
  • We have not added analytics or crash-reporting services to the App. If you let your device share usage and diagnostics data with Google, Google Play may give us aggregated crash and performance reports (Android vitals) that do not identify you.

3. Information Stored on Your Device

The App keeps the following in its private storage on your device, which other apps cannot read:

  • Projects: the name you give each project.
  • Saved items: name, area (such as "Ground floor"), item type, which dimension, size in millimetres, the ruler used, and an optional photo.
  • Settings: appearance, text size, haptics, Hán character display, ruler variants, tolerance, rounding, default input unit and handedness.
  • Purchase status: a local copy of which Google Play purchases you own, so the App also works offline.
  • Ad consent: the choice stored by Google's consent SDK (see section 6).

Project and item names may contain personal information you type, such as a client's name or address. It stays on your device unless you share it.

4. Photos

  • Adding a photo to an item is optional.
  • Take photo opens your camera app. The App itself has no camera permission.
  • Choose photo uses the Android photo picker, which gives the App only the picture you pick. The App has no access to your gallery or storage.
  • The App saves a resized copy (longest side 1600 px) in its private storage. The copy is re-encoded, so the original metadata, such as GPS location and camera details, is not kept.
  • Removing the photo, or deleting the item or its project, deletes the copy. Temporary files used while taking or sharing photos stay in the App's private cache.

5. Sharing

Data leaves the App only when you tap Share. The App prepares a text summary of the project, and optionally its photos with size captions, and hands them to the Android share sheet. You choose the receiving app, such as Zalo, Messenger or email, and that app's privacy policy applies from then on. We do not receive a copy.

6. Advertising (Google AdMob)

  • The free version shows one banner ad from Google AdMob at the bottom of the project list. There are no ads on the ruler and no full-screen ads.
  • Before any ad loads, the App uses Google's User Messaging Platform (UMP) to ask for your consent where the law requires it, for example in the EEA, the UK, Switzerland and some US states. The ad SDK starts only after that check allows it.
  • Google may collect your device's advertising ID, IP address, device and app information, and ad interactions, to deliver and measure ads, prevent fraud and, with your consent, personalize ads. See How Google uses information from sites or apps that use its services.
  • You can change your consent at any time from Privacy options on the App's About page (Settings › About Mực Thước, shown where required), and reset or delete your advertising ID in Android settings.
  • After you buy Remove ads or Unlimited projects, the App no longer starts the ad SDK and shows no ads.

7. In-App Purchases (Google Play)

  • The App sells one-time products through Google Play: Unlimited projects (which also removes ads) and Remove ads.
  • Google Play handles payment under Google's Privacy Policy. We never receive your card or payment details.
  • Google gives us limited order information, such as the order number, product, price and date, which we use for accounting, refunds and support.
  • Purchases are tied to your Google account and restored automatically when you reinstall the App.

8. Device Permissions

  • INTERNET, ACCESS_NETWORK_STATE: load ads and connect to Google Play.
  • com.android.vending.BILLING: Google Play purchases.
  • AD_ID, ACCESS_ADSERVICES_AD_ID, ACCESS_ADSERVICES_ATTRIBUTION, ACCESS_ADSERVICES_TOPICS: let the Google Mobile Ads SDK use the advertising ID and Android's Privacy Sandbox ad APIs, subject to your consent and your Android ad settings.
  • WAKE_LOCK, FOREGROUND_SERVICE: added by Google's libraries for short background tasks.

Not requested: camera, microphone, location, contacts, phone, photos and media, storage or notifications.

9. Device Backup

If you have turned on Google backup on your device, Android may include the App's data (projects, photos and settings) in the backup stored in your Google account. Google manages that backup under its own terms, and we cannot access it.

10. Children's Privacy

The App is for a general audience and is not directed at children under 13. We do not knowingly collect personal information from children, and we collect none ourselves. If you believe a child's information has been processed through the ads in the App, contact us at support@techfusion.dev.

11. Your Choices, Deletion & Rights

  • You can edit or delete any item or project at any time. Deleting a project also deletes its items and photos.
  • Clearing the App's storage in Android settings, or uninstalling the App, erases all of its data on the device. Copies in your Google backup follow your Google backup settings.
  • We hold no personal data about you on our side, and we do not sell or share personal information. Under the GDPR, CCPA/CPRA and similar laws you may still contact us with any request or question. For data Google processes for ads, use the controls in section 6 or Google's own tools.

12. Changes & Contact

We may update this Privacy Policy when the App or its third-party services change. Updates are posted on this page with a new "Last Updated" date.

  • Publisher: Techfusion Ltd, registered in Vietnam, company number 1001261052
  • Support Email: support@techfusion.dev
  • Application ID: dev.techfusion.luban