Privacy Policy

Language Stack

Effective Date: May 12, 2026

Language Stack is operated by Brindlewood LLC, doing business publicly as Brindlewood Labs (“Brindlewood,” “we,” “us,” or “our”). This Privacy Policy explains how we collect, use, store, process, share, and protect information when you use the Language Stack mobile application, website, and related services collectively referred to as the “Service.”

Language Stack is a language-learning app that helps users create study decks, import text, generate translations into target languages, create study cards, and practice using spaced repetition and related learning tools.

If you have questions about this Privacy Policy or your information, contact us at:

Brindlewood LLC
Email: support@brindlewoodlabs.com
Website: https://brindlewoodlabs.com

1. Information We Collect

We collect information needed to provide, operate, secure, maintain, and improve Language Stack.

Account Information

When you create or use a Language Stack account, we may collect and process information such as:

Email address
Account identifier or user ID
Authentication and session information
Account creation date
Sign-in and account status information
Login method and related authentication records

We use Supabase or similar backend providers to provide account authentication and backend account services.

Learning Content and Study Information

When you use Language Stack, we may collect, store, or process learning-related information, including:

Decks you create
Cards you create
Imported text passages
Words, phrases, and sentences added to study decks
Generated translations
Review history
Spaced repetition progress
Practice activity
Language selections
App preferences and settings
Reset, deletion, or account-management actions

Depending on the version of the app and enabled features, this information may be stored locally on your device, on our backend systems, or both.

Imported Text and Translation Content

If you paste, import, or submit text for translation, that text may be sent from your device to Brindlewood’s backend and then to DeepL for translation processing.

Translation-related information may include:

Source text submitted for translation
Target language selections
Generated translated text
Character counts and usage records
Request timestamps and technical metadata

Language Stack currently sends app-generated translation requests through Brindlewood’s backend to DeepL. Translation requests are not processed solely on-device.

You should not import or submit highly sensitive, confidential, medical, legal, financial, immigration, proprietary, privileged, regulated, or safety-critical information unless you understand and accept that the text may be processed through our backend systems and third-party translation infrastructure.

Translation Usage Information

We track translation usage to provide and enforce free and paid plan limits. This may include:

Account or user ID
Current usage month
Number of DeepL translation characters used
Monthly translation limit
Translation requests allowed or blocked by usage limits
Timestamps associated with usage updates
Plan status or entitlement status

Language Stack’s limits are based on DeepL translation characters, not necessarily source-text characters.

Because Language Stack may translate one source text into two target languages, one import may use roughly twice the source text length. For example, 500 source characters translated into two target languages may use about 1,000 DeepL translation characters. If additional target languages are supported in the future, usage may increase based on the number of translations generated.

Translation limits, plan features, and usage policies may change.

Subscription and Purchase Information

Language Stack may offer paid subscriptions, free trials, promotional access, or premium features through Apple’s in-app purchase system.

We do not directly collect or store your full payment-card number, Apple account password, or Apple billing credentials.

Language Stack uses RevenueCat to help manage subscription status and premium access. RevenueCat may process subscription-related and transaction-related information, including:

App user ID, anonymous ID, or other user identifier
Device and platform information
Product identifiers
Purchase history
Subscription status
Entitlement status
Free trial status
Renewal, cancellation, expiration, refund, billing retry, or grace-period status
Transaction timestamps and related metadata

We use this information to determine whether you have access to free or premium features, restore purchases, prevent fraud, troubleshoot subscription issues, understand subscription performance, and operate the Service.

Apple remains responsible for App Store payment processing, billing, subscription cancellation, and refund handling for purchases made through Apple’s in-app purchase system.

Device, Technical, Log, and Usage Information

We may collect or process technical and usage information needed to operate, secure, debug, and improve the Service, including:

Device type
Operating system version
App version
Language settings
Region
IP address or approximate location derived from IP address
Error logs
Crash reports
Diagnostic information
Performance information
Feature usage
Import counts
Character counts
Subscription status
Rate-limit information
Security events
Authentication events
Backend request metadata

We do not intentionally collect precise location data.

Support, Feedback, and Communications

If you contact us, request support, report a bug, submit feedback, respond to a survey, or send us feature suggestions, we may collect the information you provide, including your message, email address, and related support details.

2. How We Use Information

We use information to:

Provide and operate Language Stack
Create, authenticate, and manage user accounts
Generate translations and study materials
Create, store, and display decks and cards
Maintain review progress and spaced repetition functionality
Store app preferences and language selections
Track translation usage
Enforce free and paid usage limits
Determine subscription entitlement status
Restore purchases
Provide account deletion, sign-out, and reset functionality
Process support requests and communicate with users
Troubleshoot bugs, crashes, and technical issues
Prevent fraud, abuse, unauthorized access, and misuse
Secure the Service
Improve app functionality, reliability, usability, and performance
Understand how the Service is used
Comply with legal, tax, accounting, security, platform, and operational obligations
Protect the rights, safety, and security of Brindlewood, users, service providers, and the public

We do not sell your personal information for money. Some privacy laws define “sell” or “share” broadly. If those laws apply to us in the future, we will provide any required notices, rights, or choices.

3. Translation Processing and DeepL

Language Stack uses DeepL to provide translation features.

When you request a translation, the relevant text may be transmitted:

From your device
To Brindlewood’s backend services
To DeepL for translation processing
Back to the app for display and study use

Translations are provided for personal educational, language-learning, and study purposes only. Language Stack is not a professional translation service, certified translation service, legal service, medical service, immigration service, financial service, academic editing service, or professional certification tool.

Translations may be inaccurate, incomplete, awkward, misleading, culturally inappropriate, grammatically incorrect, contextually wrong, or unsuitable for your intended use. We do not guarantee that translations will be accurate, complete, reliable, culturally appropriate, or suitable for professional or high-stakes use.

You should not rely on translations generated by Language Stack for medical, legal, financial, immigration, safety-critical, emergency, academic, professional, or other important decisions. For important matters, you should consult a qualified professional, certified translator, competent native speaker, or other appropriate expert.

DeepL may process translation requests and related metadata according to its own terms, privacy policy, and data-processing practices.

4. Machine Learning and Training

We do not use your imported text, study content, or translations to train our own machine-learning models.

Text submitted for translation may be processed by DeepL according to DeepL’s own terms, privacy policy, and data-processing practices.

5. Supabase, Backend Services, and Cloud Storage

Language Stack uses Supabase or similar backend infrastructure providers for authentication, database hosting, backend functions, account records, usage tracking, and related app operations.

Information stored or processed through Supabase or similar backend systems may include:

Account identifiers and authentication records
Email address or login-related information
User IDs or anonymous identifiers
Language selections and app preferences
Translation usage records
Character usage
Plan limits and reset timing
Subscription-related entitlement status
Server logs
Technical metadata
Security-related records
Decks, cards, imported text, generated translations, review progress, or related learning data, depending on the version of the app and enabled features

We use backend systems to create and manage accounts, provide app functionality, enforce free and paid usage limits, maintain study progress where supported, secure the Service, troubleshoot bugs, prevent abuse, and operate backend features.

Full cloud sync may not be available in all versions of Language Stack. If full cloud sync is not available, some learning data may exist only on your device and may not be recoverable if lost or deleted.

As Language Stack develops, we may add, remove, or modify cloud features, including cloud sync for decks, cards, translations, review history, or other learning data. If we materially change how user data is stored or processed, we will update this Privacy Policy as appropriate.

6. Local Device Storage and Cloud Sync Limitations

Language Stack may store information locally on your device, including:

Decks
Cards
Imported text
Generated translations
Review progress
Study history
Language selections
App preferences
Cached content
Local display information related to usage

Local data may be deleted or become unavailable if you:

Delete the app
Reset content
Sign out
Delete your account
Lose access to your device
Switch devices
Experience device failure
Use an unsupported device migration process

Some local data may not be backed up or synced to our servers. If full cloud sync is not available, we may not be able to restore lost local data.

We are not responsible for loss of local data caused by app deletion, device loss, reset actions, sign-out, account deletion, user error, system failure, unsupported migration, or lack of cloud sync.

7. Translation Character Limits

Language Stack may provide free and paid translation allowances. We may track translation usage, including character counts, request timestamps, plan status, and account identifiers, to enforce applicable limits and prevent abuse. The specific limits available to your account will be shown in the app and may vary by plan, subscription status, promotional access, technical constraints, or product changes.

These limits refer to DeepL translation characters, not necessarily source-text characters.

Because Language Stack may translate into two target languages, the number of DeepL translation characters used may be approximately double the source text length. If additional target languages are supported in the future, usage may increase further depending on how many translations are generated.

Translation limits, plan features, and usage policies may be changed, reduced, expanded, suspended, or discontinued at any time for technical, business, cost, security, abuse-prevention, or product reasons.

8. Subscriptions, Apple, and RevenueCat

Language Stack may offer paid subscription plans, free trials, promotional offers, or premium features through Apple’s in-app purchase system.

Paid features may include higher DeepL translation character limits, additional study features, pronunciation or audio features, additional target-language options, or other premium functionality.

Subscription billing, cancellation, renewals, refunds, and payment processing are handled by Apple according to Apple’s terms and policies. We do not directly receive or store your full payment-card information, Apple account password, or Apple billing credentials.

Language Stack uses RevenueCat to help manage subscription entitlement status and premium access. RevenueCat may process subscription identifiers, product identifiers, entitlement status, renewal status, cancellation status, refund status, trial status, transaction timestamps, and related purchase metadata.

We use this information to:

Determine whether you have access to free or premium features
Restore purchases
Troubleshoot subscription issues
Prevent fraud and abuse
Understand subscription performance
Operate and improve the Service

Deleting your Language Stack account does not necessarily cancel an active Apple subscription. To avoid future charges, you must cancel your subscription through your Apple account settings. If you delete your Language Stack account but do not cancel your Apple subscription, Apple may continue billing you according to Apple’s subscription terms.

Subscription features, pricing, limits, and availability may change over time, subject to applicable law and Apple’s rules.

9. Text-to-Speech and Audio Features

The current DeepL translation character limit applies to text translated through DeepL.

Text-to-speech, pronunciation playback, audio, voice, speech-to-text, or other audio-related features, if added in the future, may have separate usage rules, limits, pricing, processing practices, or third-party service providers.

If we add audio or text-to-speech features that materially change how information is processed, we will update this Privacy Policy as appropriate.

10. How We Share Information

We may share information with service providers and third parties as needed to operate, secure, maintain, and improve Language Stack, including:

Supabase or similar backend providers for authentication, database hosting, backend functions, storage, account services, and usage tracking
DeepL for translation processing
RevenueCat for subscription entitlement management and purchase-status tracking
Apple for App Store distribution, in-app purchases, subscriptions, refunds, platform services, and app review
Hosting, security, analytics, crash-reporting, customer-support, email, and operational service providers
Legal, regulatory, law-enforcement, or government authorities when required or permitted by law
Professional advisors, such as attorneys, accountants, insurers, or auditors
A successor organization in connection with a merger, acquisition, financing, reorganization, sale of assets, or similar business transaction

These providers may process information according to their own privacy policies, security practices, service terms, and data-processing practices.

We do not sell your personal information for money. We do not knowingly sell or share personal information of children under 16. Some privacy laws define “sell” or “share” broadly. If those laws apply to us in the future, we will provide any required notices, rights, or choices.

11. Data Retention

We retain information for as long as reasonably necessary to provide the Service, maintain your account, enforce usage limits, provide subscriptions, comply with legal obligations, resolve disputes, prevent fraud or abuse, maintain security, and operate our business.

Different types of information may be retained for different periods. For example:

Account information may be retained while your account is active.
Study content may be retained while your account exists or until deleted, subject to app functionality and backup limitations.
Subscription and transaction metadata may be retained as needed for billing records, entitlement verification, fraud prevention, accounting, tax, legal, and dispute-resolution purposes.
Translation usage records may be retained as needed to enforce usage limits, prevent abuse, troubleshoot errors, and maintain records.
Logs and security records may be retained for a limited period unless longer retention is needed for security, fraud prevention, legal compliance, or operational reasons.
Backup copies may persist for a limited time after deletion before being overwritten or deleted in the ordinary course of business.

Local data may remain on your device until you delete the app, reset content, sign out, delete your account, or otherwise remove it.

12. Account Deletion, Sign Out, and Reset All Content

Language Stack may provide several different account and data actions. These actions are not the same.

Sign Out

Signing out ends your current session. In some versions of the app, signing out may remove local learning data from the device because full cloud sync may not be available.

Signing out does not delete your account and does not cancel any active Apple subscription.

Reset All Content

Resetting all content deletes local learning or study content and allows you to start over. It does not necessarily delete your account and does not cancel any active Apple subscription.

Delete Account

Deleting your account is intended to permanently remove your Language Stack account and associated server-side account data, subject to limited retention obligations described in this Privacy Policy.

When you delete your account, we will take steps to delete or de-identify account information associated with your account, unless we are required or permitted to retain certain information for legal, security, tax, fraud-prevention, dispute-resolution, backup, operational, or compliance reasons.

Account deletion may remove:

Your account/authentication record
Server-side usage records associated with your account
Server-side learning data associated with your account, where applicable
Local learning data stored on your device, where applicable

Some information may remain temporarily in backups, logs, transaction records, security records, or records maintained for legal, tax, accounting, fraud-prevention, operational, or compliance purposes.

Deleting your Language Stack account does not necessarily cancel an active Apple subscription. To avoid future charges, you must cancel your subscription separately through your Apple account settings.

Account deletion is different from signing out, deleting the app, resetting local content, or canceling an Apple subscription.

13. User-Imported Content and Sensitive Information

You are responsible for the text, words, phrases, sentences, documents, and other content you import, paste, create, or store in Language Stack.

You should not use Language Stack to import, submit, store, or process content that:

You do not have the right to use
Violates laws or third-party rights
Contains highly sensitive personal information
Contains passwords, API keys, payment-card data, Social Security numbers, government identification numbers, protected health information, or financial account details
Contains confidential professional, legal, medical, financial, immigration, proprietary, privileged, or regulated information that you do not want processed by third-party services
Contains unlawful, abusive, exploitative, or harmful material

Language Stack is designed for personal language-learning use. It is not designed to be a secure storage system for confidential records or a professional translation system for high-stakes documents.

14. Children’s Privacy

Language Stack is not intended for children under 13. We do not knowingly collect personal information from children under 13.

If we learn that we have collected personal information from a child under 13, we will take reasonable steps to delete it.

If you are between 13 and the age of majority in your jurisdiction, you should use Language Stack only with permission from a parent or guardian.

If you believe that a child under 13 has provided personal information to us, contact us at:

support@brindlewoodlabs.com

15. Security

We use reasonable administrative, technical, and organizational safeguards designed to help protect information.

However, no method of transmission, storage, or processing is completely secure. We cannot guarantee that unauthorized access, disclosure, loss, misuse, alteration, or destruction will never occur.

You are responsible for maintaining the security of your device, login credentials, Apple account, and email account.

16. International Processing

Your information may be processed in the United States and in other locations where we or our service providers operate.

By using Language Stack, you understand that your information may be transferred to, stored in, or processed in locations outside your state, province, or country. These locations may have data-protection laws different from those in your jurisdiction.

17. Your Choices and Rights

Depending on your location and applicable law, you may have rights to:

Access certain personal information
Correct certain personal information
Delete your account
Request information about how your data is used
Object to or restrict certain processing
Opt out of certain communications

To make a privacy request, contact us at:

support@brindlewoodlabs.com

We may need to verify your identity before responding to a request.

Some rights may be limited by applicable law, security requirements, fraud-prevention needs, technical limitations, or our legal and operational obligations.

18. U.S. State Privacy Rights

Depending on where you live and whether applicable privacy laws apply to Brindlewood, you may have additional rights regarding your personal information.

We do not sell your personal information for money.

We do not knowingly sell or share personal information of children under 16.

Some privacy laws define “sell” or “share” broadly. If those laws apply to us in the future, we will provide any required notices, rights, or choices.

If we become subject to additional state privacy requirements, we will update this Privacy Policy and provide any required notices, rights, or request mechanisms.

19. Changes to This Privacy Policy

We may update this Privacy Policy from time to time.

If we make material changes, we may notify you through the app, website, email, or other reasonable means. The “Effective Date” above indicates when this Privacy Policy was last updated.

Your continued use of Language Stack after an updated Privacy Policy becomes effective means the updated policy applies to information collected after the effective date, to the extent permitted by law.

If you do not agree with the updated Privacy Policy, you should stop using the Service.

20. Contact Us

If you have questions about this Privacy Policy, your information, or your privacy choices, contact us at: