Terms of Service

1. Scope and Operator

These Terms of Service apply to the use of the language learning platform Langsi, accessible at www.langsi.app, and all associated mobile apps and services.

2. International availability and analytics

Langsi is an internationally available language-learning service operated by Data Informed Decisions LLC, Florida, USA. Availability of particular interface or learning languages does not indicate geographic targeting; languages are offered to users worldwide regardless of their location. Subscription prices are stated in US dollars.

Information on analytics and data processing is provided in the Privacy Policy.

3. Description of Services

Langsi is a web-based SaaS language learning platform offering:

• AI-powered vocabulary learning with spaced repetition (Leitner method)
• Multilingual learning modes (flashcards, multiple choice, listening)
• Daily learning sessions with personalized goals and streaks
• AI-generated example sentences, explanations and coaching messages
• Text-to-speech pronunciation for vocabulary and example sentences
• Topic-based audio trainers and exercises
• Progress statistics and learning analytics

The available feature set depends on the user's selected plan.

4. Registration and User Account

Registration with a valid email address and password, or via Google OAuth, is required to use Langsi. The user affirms that the information provided at registration is truthful. The user account is non-transferable. The user is obliged to keep access credentials confidential and notify the operator immediately of any suspected misuse. Users must be at least 13 years old. Users aged 13 to 15 may use Langsi only with the consent of a parent or legal guardian.

5. Free Services (Free Plan)

Langsi offers a free basic access including:

• Access to one selectable language
• Daily learning goal of up to 40 vocabulary items per day
• All basic learning modes (flashcards, multiple choice, listening)
• Learning streak and progress statistics

The operator reserves the right to adjust the free scope at any time. Existing free plan users will be notified at least 14 days in advance of material restrictions.

6. Paid Services (Premium Subscriptions)

Langsi offers the following paid plans:

Current prices are displayed on the Langsi pricing page and apply from the time of contract conclusion.

7. Subscriptions and Contract Terms

Subscriptions are billed on a monthly or annual basis. The subscription automatically renews for the selected billing period unless cancelled in time. Cancellation: The subscription can be cancelled at any time at the end of the current billing period via: Profile > Subscription > Manage Subscription > Cancel, or by email to: info@data-informed-decisions.com. After cancellation, access remains until the end of the paid period.

8. Payment Processing (Stripe)

Payment processing is handled by Stripe (Stripe, Inc.). Accepted payment methods are shown at checkout. On failed payment, Langsi reserves the right to temporarily restrict access to paid features until the outstanding amount is settled.

9. Cancellation period and refunds

You may withdraw from a paid subscription within 14 days of your initial purchase of a plan without giving any reason and receive a full refund. To withdraw, send us a clear statement within this period, for example by email to info@data-informed-decisions.com. You may use the model form below, but this is not required. Outside this period, refunds may be granted at our discretion on a case-by-case basis.

10. Limitation of Liability

To the extent permitted by applicable law, Langsi is provided “as is” and “as available”. We are not liable in particular for the accuracy, completeness or timeliness of AI-generated vocabulary, translations and explanations; for individual learning success; for data loss caused by the user; or for damage caused by third-party providers (such as Stripe, Google or Resend) outside our control. Our total liability arising out of or in connection with these Terms is limited to the amounts you paid us in the 12 months before the event giving rise to the claim. Nothing in these Terms limits liability that cannot be limited under applicable law.

11. Governing Law and Jurisdiction

These Terms are governed by the laws of the State of Florida, USA, excluding its conflict-of-law rules and the United Nations Convention on Contracts for the International Sale of Goods. Mandatory consumer-protection laws of the country in which you reside remain unaffected. The place of jurisdiction is Fort Lauderdale, Florida, USA, unless mandatory law provides otherwise.

12. Severability Clause

Should individual provisions of these Terms of Service be or become invalid or unenforceable, this shall not affect the validity of the remaining provisions. The invalid provision shall be replaced by a provision that comes closest to the economic purpose of the invalid provision. These Terms are available in several languages. The English version is binding; translations are provided for convenience.