Privacy Policy
Last updated October 12, 2026
1. Who we are
2Sigma is an exam-preparation service for students in Advanced Placement courses. We decide why and how your personal data is processed, which makes us the controller of that data under the EU General Data Protection Regulation (GDPR) and a business under the California Consumer Privacy Act as amended by the CPRA, and the equivalent state privacy laws that follow it.
2Sigma is run from the United States by a sole proprietor, not by an incorporated company, so there is no company registration number to give. That sole proprietor is the controller of your data.
For anything in this policy, including any request about your data, write to [email protected]. We have not appointed a Data Protection Officer; this address reaches the person responsible for privacy.
2. What we collect
Everything below is data we actually hold. Nothing on this list is optional telemetry we could switch off and still run the service, except where marked.
| Category | What it is | Where it comes from |
|---|---|---|
| Account identity | Email address, password (stored only by Firebase, never by us), display name, and a Firebase user ID | You, at sign-up, or your Google account if you sign in with Google |
| Course enrolment | Which courses you are enrolled in and when | Your use of the service |
| Answers | The text you type as an answer, and the flattened PNG of anything you draw on the practice canvas | You, when you submit an answer |
| Evaluations | The score, written feedback and inline comments our AI evaluator produced for each answer | Generated when you submit |
| Mastery scores | A score per topic and per sub-topic, and the questions you have skipped | Derived from your answers |
| Tutor conversations | Your full conversation with Sigmund, our AI tutor, stored per practice session | You, while you practise |
| Subscription and usage | Your plan, its billing period and status, the PayPal subscription it is billed through, the record of every solution and chat message you spend against a monthly allowance, and coupon redemptions | Your subscription and your practice |
| Technical logs | Structured server logs for abuse and cost control, including your IP address on the anonymous landing-page chat | Automatically, on every request |
| Analytics and diagnostics | Product analytics events, error reports, performance traces, error-triggered session recordings, and recordings of your sessions while you practise, together with your device type, your approximate location (the city, worked out from your connection) and the link that brought you to the site | Automatically — subject to your consent, see section 5 |
We do not collect your date of birth, national ID number, address, or payment card details. Card details go directly to PayPal and never reach our servers.
The anonymous chat on our landing page is not stored. The transcript stays in your browser and is sent to our AI provider for each reply; we keep no copy.
3. Why we use it, and our legal basis
| What we do | Why | Legal basis (GDPR Art. 6) |
|---|---|---|
| Create and run your account | To give you the service you asked for | Performance of a contract |
| Serve questions, evaluate answers, run the tutor | The service itself | Performance of a contract |
| Track mastery and pick your next question | The adaptive part of the service | Performance of a contract |
| Take payment, run your plan and its monthly allowances | To provide the service you subscribed to | Performance of a contract |
| Keep accounting records of payments | US federal and state tax and bookkeeping rules | Legal obligation |
| Rate-limit, detect abuse, keep the service secure | To stop the service being abused, and to control the cost of AI calls | Legitimate interests |
| Monitor errors and performance | To find and fix faults | Legitimate interests |
| Product analytics and session recording | To understand how the product is used and improve it | Consent |
Where we rely on legitimate interests, we have balanced them against your rights; you can object at any time (section 9).
4. Artificial intelligence
The tutor ("Sigmund"), the answer evaluator and the landing-page questionnaire are all powered by a large language model provided by Anthropic. This means that the questions you are served, the answers you write, the drawings you submit and every message you send the tutor are transmitted to Anthropic so that a reply or a grade can be generated.
AI output can be wrong. Scores, feedback and explanations are not a guarantee of correctness or of any exam result, and no decision with a legal or similarly significant effect on you is made by automated means.
Please do not type personal details about yourself or anyone else into the tutor or the landing-page chat. Nothing in the service requires them.
5. Analytics, error monitoring and session recording
- Google Analytics 4. We send product events (page views, practice events, subscription funnel) tagged with your Firebase user ID and non-identifying user properties such as your interface language, active course and your plan tier. We never send your email address or name to Google Analytics. Analytics data is exported to Google BigQuery, and that export dataset is located in the United States.
- Sentry. Errors, stack traces and a sample of performance traces. These run on our legitimate interest in keeping the service working, and are not consent-gated. Sentry Session Replay — a replay of a browsing session in which an error occurred — follows your analytics choice below, and stops the moment you turn analytics off. Every replay is captured with all text and all form input masked and all media blocked, so a replay of the practice screen does not show what you wrote or drew.
- PostHog. A recording of your session while you go through the onboarding and while you practise, so that we can watch how the product is actually used and fix what gets in the way. Unlike the Sentry replay, this recording is readable: it shows the page as you saw it — the question, your conversation with the tutor, what you typed and what you drew on the canvas — together with your clicks, scrolling and mouse movement. What it never captures is your password or email as you type them, a coupon code, the PayPal payment form, or your name, email address and profile picture where the app displays them. A recording is tagged with your Firebase user ID and whether you are a guest, never with your email address or name, and carries a few product events as markers on its timeline. Alongside it PostHog works out your approximate location (the city) from your connection, notes your device type, and receives the link that brought you to the site — its campaign tags and the site that referred you. It follows your analytics choice below and stops the moment you turn analytics off. For each student we have a recording of, we keep a working page in Notion that puts those details next to your tutor conversation and your practice results, labelled with your user ID, and a short daily summary of it is posted to our internal Discord, labelled with a shortened user ID.
- LaunchDarkly. Feature-flag evaluation receives your Firebase user ID and your email address, which is what lets us switch a feature on for a defined group of accounts rather than for everyone. It also receives your display name.
- Resend. When a paid plan starts we email you a confirmation of it, from [email protected]. Resend receives your email address, your display name if your sign-in provider gave us one, and the content of that message, in order to deliver it. This is a service message we send to perform our agreement with you, not marketing, so it is not part of the analytics choice below and there is nothing to unsubscribe from; we will ask for your consent separately before ever sending you anything else.
How the choice works. Where you are decides how we ask. In the EU/EEA, the UK and Switzerland, nothing in this section runs on your first visit: no request is made to Google Analytics and no replay or session recording is made until you decide, and the banner offers accept all and reject all next to each other, one click each. Everywhere else, analytics runs from your first visit without a banner; this policy is the notice, and you can opt out at any time and we stop. Either way your decision — what you chose and when — is stored in the consent cookie listed in the next section, so that it can be evidenced later. You can change it at any time from Cookie settings in the page footer, or under Privacy in your account settings; a withdrawal takes effect immediately and stops all of it.
LaunchDarkly is not part of that choice: it decides which version of the product you are shown, so it runs on our legitimate interest and sets no cookies.
6. Cookies
We use a small number of cookies, and that is the whole list.
| Cookie | Set by | What it does | Lifetime |
|---|---|---|---|
__session | Us | Keeps you signed in. Strictly necessary — without it the service cannot tell who you are | 5 days |
2sigma_consent | Us | Stores the analytics choice you made and when you made it, and keeps the banner from asking again | 12 months |
_ga, _ga_<id> | Google Analytics | Tells visitors and sessions apart for the usage statistics | up to 2 years |
The first two are strictly necessary or set at your own request, so they do not depend on consent — but none of them tracks you across other websites. The Google Analytics cookies follow the choice described above: in the EU/EEA, the UK and Switzerland they are set only after you accept, never before; elsewhere they are set from your first visit until you opt out. Sentry sets no cookies; Session Replay keeps its state in the browser tab's session storage. PostHog sets no cookies either: it keeps the identifiers that tie a recording together in your browser's local storage, and only once a recording has started.
7. Who else sees your data
We use the following providers. Except where noted, each acts as a processor that may only handle your data on our instructions.
| Provider | What it receives | Role |
|---|---|---|
| Anthropic | Every question, answer, drawing and tutor message | Processor |
| Google (Firebase Authentication) | Email address, display name, user ID | Processor |
| Google (Analytics 4 and BigQuery) | User ID and event parameters | Processor |
| Sentry | Errors, traces and error-triggered session replays | Processor |
| PostHog | Recordings of your onboarding and practice sessions, your user ID, and product events, together with your approximate location derived from your connection, your device type, and the link that brought you to the site | Processor |
| LaunchDarkly | User ID, email address, display name | Processor |
| Resend | Your email address, display name, and the content of your subscription confirmation | Processor |
| Hetzner | Hosting of the application and the entire database | Processor |
| Cloudflare (R2) | Exam and question assets only — no student data | Processor |
| Notion | A page for each student we have a recording of, holding your tutor conversation, practice results, device, approximate location and the link that brought you, labelled with your user ID | Processor |
| Discord | Operational alerts, and a daily summary of each recorded student's activity, labelled with a shortened user ID and linking to that student's Notion page — the recordings themselves stay with PostHog | Processor |
| PayPal | Your name, email address and payment details, when you subscribe to a paid plan | Independent controller — PayPal handles your payment under its own privacy policy |
We do not sell your personal data and we do not share it for advertising.
Several of these providers are outside the European Economic Area, mostly in the United States. Those transfers rely on each provider's own data processing terms and on the Standard Contractual Clauses they incorporate, and — where the provider is certified under it — on the EU–US Data Privacy Framework.
8. How long we keep it
We do not run a fixed deletion schedule yet, so what you create stays while your account does. Your account, your answers and drawings, your mastery scores and your tutor conversations are kept for as long as your account is open, and go when you delete it or ask us to — section 9 explains how.
Two things outlive that. Records of what you bought are kept for as long as US federal and state tax and bookkeeping rules require, which is why deleting your account does not remove them. Your consent record is kept while we still rely on it, and for a period afterwards, so that we can show what you chose and when.
Technical logs, analytics data, error reports and session recordings are held by the providers named in sections 5 and 7 under their own retention settings.
One copy does run on a clock. The page we keep for you in Notion (section 7) is deleted 90 days after you were last seen on the service, and sooner if you delete your account.
We are working on fixed retention periods and will state them here once they are set.
9. Your rights
You have the right to access your data, to have it corrected, to have it erased, to receive a copy in a portable format, to restrict or object to processing, and to withdraw any consent you have given (withdrawal does not affect processing already carried out). Under US state privacy laws such as the CCPA you have the right to know what personal information we hold about you, to have it corrected or deleted, and not to be treated differently for exercising those rights. We do not sell or share your personal information as those laws define it.
Two of these you can exercise yourself, immediately, from your profile menu → Settings: "Download my data" gives you a single JSON file with everything we hold about you, and "Delete my account" erases it. Neither needs our approval and neither waits on us. For anything else — correction, restriction, objection, or withdrawing a consent — email [email protected] and we will respond within 30 days.
Deleting your account erases your record and everything attached to it from our database, your tutor conversations, your Firebase authentication record, your data held by our analytics, error-monitoring and session-recording providers, and the page we keep for you in Notion. PayPal is an independent controller, so a request about the data PayPal holds has to go to PayPal.
If you think we have handled your data badly, please tell us first. You may also complain to the US Federal Trade Commission or your state attorney general, or — if you are in the EU or the EEA — to the data protection supervisory authority where you live.
10. Security
Access to the production database is limited to the people who need it, staff access to internal tools is logged, and traffic to the service is encrypted in transit. No service is perfectly secure; if a breach affects your data we will notify you and the relevant authority as the law requires.
11. Age
The service is for people aged 18 and over. We do not knowingly collect data from anyone younger. If you believe a minor has an account, write to us and we will delete it.
12. Changes
If we change this policy we will update the date at the top of this page, and we will tell you directly about any change that materially affects your rights.