流
Liu
Getting things ready
Preparing your next step.
“Fluency is built one remembered word at a time.”
Preparing your next step.
“Fluency is built one remembered word at a time.”
Legal
This policy explains what information Liu collects, why we use it, how long we keep it, and the choices available to you.
Effective date: July 17, 2026
This Privacy Policy applies when you use Liu's website, installable web app, account features, learning tools, paid services, referrals, support channels, and related services.
Depending on how you use Liu, you may provide account information, such as an email address, display name, password, date of birth, student-verification information, profile preferences, learning settings, custom cards or sets, support messages, gift notes, and referral information.
Passwords are handled through Liu's authentication provider and are not available to Liu in readable form. Payment-card details are collected and processed by Stripe rather than stored directly by Liu.
Liu records information needed to operate the service, including account identifiers, authentication and security state, legal-policy acceptance, HSK placement and learning progress, review history, streaks, rewards, economy balances, subscription and entitlement status, referral progress, device-notification state, and technical logs.
Liu may calculate first-party progress summaries and derived learning insights from this activity. These may include active study days, estimated engaged study time, estimated sessions, answer totals, aggregate accuracy, question-type and HSK-level patterns, vocabulary saved or created, daily-target completions, streak milestones, and similar recap statistics.
Personalized dashboards and learning recaps are generated from Liu's own application records. They remain available even when optional PostHog analytics is declined because those first-party records are needed to provide progress, history, and recap features.
We may also receive basic technical information such as browser type, operating system, approximate network location, request timestamps, error details, and security signals. We use this information to keep Liu reliable, prevent abuse, troubleshoot problems, and comply with legal obligations.
With your permission, Liu uses PostHog to understand how people move through signup, onboarding, studying, subscriptions, purchases, referrals, progress summaries, and learning recaps. Optional analytics does not affect your ability to use Liu.
Product-analytics events may include a pseudonymous Liu account identifier, browser and device information, page views, page exits, product surfaces viewed, web-performance measurements, account tier, HSK level, question category, aggregate study outcomes, normalized error categories, transaction or referral status, and whether a learning recap was offered, viewed, completed, dismissed, revisited, shared, or followed by a study action.
Recap analytics may use broad or bucketed categories, such as a range of active days or reviews, rather than the personalized recap's exact contents. Liu does not intentionally send PostHog the highlighted vocabulary, personalized recap slides, raw learning history, or raw identifiers used to generate a recap.
Liu uses selected, purpose-built analytics events. Broad automatic click and form-field capture, session replay, and heatmaps are disabled. Liu's PostHog project is also configured to discard client IP data from analytics storage.
Network, hosting, and security providers may still temporarily process an IP address as technically necessary to transmit and protect an internet request, even where an analytics provider is configured not to retain that address as analytics data.
Liu does not intentionally send PostHog passwords, authentication codes, access tokens, payment-card details, dates of birth, email addresses, display names, usernames, raw study answers, raw word identifiers, search text, custom-card content, custom-card notes, example sentences, gift notes, notification body text, friend user identifiers, or raw referral codes.
You may allow, decline, or later withdraw analytics consent through Liu's consent banner or Settings. Withdrawing consent stops future analytics collection from Liu on the affected account or device.
You may also request deletion of analytics associated with your Liu account. Analytics deletion is processed separately from ordinary consent withdrawal because withdrawing consent stops future collection but does not by itself erase information collected while consent was active.
Liu uses PostHog's United States cloud region. Browser analytics requests are routed through Liu's first-party proxy domain,flow.goliu.app, before being delivered to PostHog for processing on Liu's behalf.
Liu uses necessary browser storage for authentication, security, preferences, legal acceptance, installable-web-app behavior, and remembering your analytics choice. Optional PostHog cookies or local storage are enabled only after you allow analytics.
More information is available in our Cookie & Analytics Notice.
We use information to:
Liu relies on service providers to operate the product. These may include Supabase for authentication and database services, Vercel for hosting, Stripe for payment processing, Resend for email delivery, Sentry for error monitoring, Cloudflare for security checks, PostHog for optional product analytics, and other infrastructure providers described in Liu's legal and third-party notices.
Providers receive only the information reasonably needed to perform their services and process it under their applicable contractual, privacy, and legal obligations.
Where applicable law requires a legal basis, Liu processes information as necessary to provide the service you request, protect Liu and its users, comply with law, and pursue legitimate operational interests that do not override your rights. Optional product analytics relies on your consent where consent is required.
Liu automatically summarizes your own activity to show progress, patterns, milestones, and areas you may wish to review. These summaries do not determine eligibility for education, employment, credit, insurance, housing, or other similarly significant decisions.
You may withdraw analytics consent at any time without affecting the lawfulness of processing that occurred before withdrawal.
Liu keeps information only as long as reasonably needed for the purposes described in this policy, including providing the service, maintaining security, resolving disputes, honoring purchases, and meeting legal obligations.
First-party learning history, daily learning rollups, and generated progress summaries may be retained while your account remains active because they support dashboards, review history, learning progress, and recap features. A generated recap may be recalculated from those records instead of being retained as a permanent separate copy.
Optional product-analytics information is retained according to Liu's analytics settings, operational needs, deletion processes, and the storage practices of the applicable service provider. Liu generally analyzes optional product analytics within a rolling 12-month period and may delete or aggregate analytics when it is no longer reasonably needed.
Verified account and analytics deletion requests may cause eligible information to be deleted earlier. Some transaction, fraud-prevention, legal-acceptance, and security records may be retained longer when reasonably necessary or required by law.
You may use Liu's account-deletion tools to request deletion of your Liu account and associated application data, subject to limited information that must be retained for legal, security, fraud, or transaction-record purposes.
Eligible account deletion removes first-party learning rollups and recap-ready application records tied to the deleted account. It also prevents Liu from generating new personalized recaps for that account.
When an eligible account-deletion request is completed, Liu submits the account's pseudonymous PostHog identifier for deletion together with associated analytics events. This provider-side deletion may be completed asynchronously.
You may also request deletion of account-associated analytics without deleting your Liu account through Settings or by contacting support. Deleting optional analytics does not delete the first-party learning history that remains necessary to operate your Liu account.
Depending on where you live, you may have rights to access, correct, delete, restrict, or receive a copy of certain personal information, object to certain processing, or withdraw consent. We may need to verify your identity before completing a request.
Personalized recaps are private by default. Any sharing feature requires an affirmative action from you, and you can review the shareable result before sending or posting it.
You can update many account and privacy settings directly in Liu. Additional requests may be sent to the support address below.
Liu is not intended for children under 13. We may apply a higher minimum age where required by local law. If we learn that an ineligible child provided personal information, we will take reasonable steps to remove it.
Liu uses administrative, technical, and organizational safeguards designed to protect information. No online service can guarantee absolute security.
Liu and its providers may process information in the United States and other countries. Where required, appropriate contractual or legal safeguards are used for international transfers.
We may update this policy as Liu changes. The effective date above identifies the current version. When required, Liu will provide additional notice or ask you to acknowledge a revised policy.
Privacy questions and requests can be sent to support@liu.app.