LangPrizm Privacy Policy
Effective date: October 16, 2026
LangPrizm helps you read books and web articles in another language, translate words and sentences, and practice the words you save. This policy explains what data the app and its translation service handle, why, and what control you have.
Who we are
LangPrizm is operated by Strandbyte s.r.o., Uralská 689/7, 160 00 Praha 6 – Bubeneč, Czech Republic, company ID (IČO) 24518077 ("we", "us"). We are the controller for the personal data described here. Contact us about privacy at info@strandbyte.com.
The short version
- Your books, saved articles, vocabulary, notes, and review history stay on your device. We do not receive them.
- When you ask for a live translation, the text you selected is sent through our server to a translation provider and is not stored by us.
- Live translation needs a free account created with Sign in with Apple. We do not ask Apple for your name or email.
- No advertising, no tracking across apps or websites, and no analytics SDKs.
What stays on your device
Books you import, articles you save, your vocabulary, sentences, highlights, notes, bookmarks, review history, settings, and the app's translation cache are stored only in the app on your device. Deleting the app deletes them. Deleting your translation account (see below) does not delete them.
Reading, reviewing, and translations already cached on your device work without an account.
Live translation
When you tap a word or sentence and ask for a translation, the app sends to our translation service (a server we run on Cloudflare):
- the selected word or sentence, and the source and target language codes;
- for a word, its dictionary form if the device determined one.
Our service forwards this to Microsoft Azure Translator to produce the translation. For some words the service also translates dictionary results through English.
For Czech, Italian, Portuguese, Dutch, Polish, Russian, Swedish, Danish, Finnish, Greek, and Hungarian, the service also sends the single tapped word to OpenAI to find its dictionary form (for example, the infinitive of a verb). The sentence around the word is sent to OpenAI only if you tap the explicit "retry using the sentence" button next to a base form.
We do not send your book's title or author, the rest of the book or article, or full web page addresses. The sentence around a tapped word stays on your device unless you translate that sentence or use the retry button described above.
Our service does not store the text you translate or the translations it returns, and keeps no translation cache on the server.
- Microsoft: we use Azure Translator's European endpoint. Microsoft states that text translation does not store the text it receives (Translator data, privacy, and security).
- OpenAI: we use OpenAI's API with response storage turned off. Under OpenAI's API terms, this data is not used to train OpenAI's models, and OpenAI keeps abuse-monitoring logs for up to 30 days unless the law requires longer (OpenAI API data controls). OpenAI processes it in the United States.
Your translation account
To prevent abuse and keep costs fair, live translation requires a free account. You create it with Sign in with Apple. The app requests no name or email, so we receive only Apple's app-specific identifier for you.
Our service stores:
- that identifier, your allowance plan, and the account's status;
- encrypted Apple credentials needed to keep you signed in and to revoke access when you delete the account;
- one-way hashes of the app's session tokens (never the tokens themselves). Sessions last up to 30 days and renew while you use the app;
- a daily character count used to enforce the free daily allowance. It is stored under a pseudonym derived from your account and the date, and contains no text.
On your device, the session is kept in the iOS Keychain and does not leave the device in backups.
Other connections the app makes
- Project Gutenberg (gutenberg.org): when you browse or search Discover and download a free book, the app requests the catalog and the book directly from Project Gutenberg. Your search terms, the chosen language, and your IP address reach Project Gutenberg, which applies its own privacy policy.
- Browser: web pages load directly from the websites you visit, which can see your IP address. Text typed into the address bar that is not a web address is sent to DuckDuckGo as a search. The browser keeps no history and no cookies after you leave it, and translations of web pages are kept only in memory.
- Apple: Sign in with Apple is provided by Apple under Apple's privacy policy.
Why we process data (legal bases)
- To provide live translation and your account: performance of our agreement with you (GDPR Art. 6(1)(b)).
- To enforce the daily allowance, prevent abuse, and keep the service secure: our legitimate interest in running a free service sustainably (Art. 6(1)(f)).
Service providers and transfers
We use these providers to run the service: Cloudflare (our server and its database), Microsoft (Azure Translator), and OpenAI (dictionary forms for the languages listed above). They are based in the United States. Our server runs on Cloudflare's global network, so a request may be handled in the data center nearest to you; our database is stored in Cloudflare's Eastern Europe region. Where personal data is transferred outside the EU/EEA, we rely on the EU–US Data Privacy Framework for providers certified under it, and otherwise on the European Commission's Standard Contractual Clauses in the provider's data processing agreement. Sign in with Apple is operated by Apple under Apple's own privacy policy.
How long we keep data
- Translated text: not stored by us.
- Daily character counts: until shortly after the end of the day (UTC), then deleted automatically.
- Sign-in challenges: 5 minutes. Session tokens: up to 30 days after last use.
- Account data: until you delete your account.
- Server logs: for each request our service writes a short technical record (a random request ID, the endpoint, the result status, and the duration) and error types. These records never contain translated text, account identifiers, or tokens, and we do not store them (log storage and log export are turned off for our server).
- Backups: our database provider keeps point-in-time recovery data for up to 30 days, after which deleted records are gone from backups too.
Deleting your account
In the app, go to Settings → Translation Account → Delete Cloud Account. We immediately end all sessions, revoke the Apple sign-in grant, and delete the account and its credentials. If Apple's service is temporarily unavailable, deletion stays pending and is retried automatically; the app shows its status. The current day's pseudonymous character count is kept until the day ends (UTC), so deleting and re-creating an account does not reset the daily allowance. Your books and learning data on the device are not affected.
You can also revoke the app's access at any time in iOS Settings → [your name] → Sign in with Apple.
Your rights
You can ask us for access to your data, correction, deletion, restriction, or portability, and you can object to processing based on legitimate interests. Email info@strandbyte.com. Because we hold almost no data about you, the fastest way to delete everything we have is the in-app account deletion above. You may also complain to the Czech data protection authority, the Úřad pro ochranu osobních údajů (www.uoou.cz), or to the authority where you live.
Children
LangPrizm is not directed to children under 13, and we do not knowingly create accounts for them.
Beta testing
If you test LangPrizm through Apple's TestFlight, Apple may share crash reports and any feedback you choose to send with us, under Apple's TestFlight terms. We use them only to fix problems.
Changes
We will update this policy when the app's data handling changes and change the effective date above. Significant changes will be announced in the app or its release notes.