Terms of Service

Brownian Bridge (www.brownian-bridge.com, “the Service”) is operated by Benoit Vandevelde, trading as Brownian Bridge, a sole trader established in the United Kingdom (“we”, “us”). Our address is Flat 204 Hampton Apartments, Duke of Wellington Avenue, London SE18 6NX, United Kingdom, and you can email us at contact@brownian-bridge.com.

These terms are the contract between you and us when you create an account or buy Premium. Please read them together with our Privacy Policy and our Refund & Cancellation Policy. They are available in English only.

A “consumer” is an individual acting wholly or mainly outside their trade, business, craft or profession. Where a section applies differently to consumers and to business customers, it says so.

• You must be at least 16 to create an account and at least 18 to buy a Premium subscription.
• Give accurate information, keep your password secure, and tell us promptly if you think someone else has used your account.
• An account is for one person. Do not share your login or let anyone else use your Premium access.
• You are responsible for activity under your account, unless it happened because we failed to keep the Service reasonably secure.

Part of the Service is free. Premium unlocks the additional material described on the Pricing page when you subscribe: every advanced lesson, all interactive labs and notebooks, worked solutions to quiz questions, the full Brain Teaser Academy and interview question bank, and unlimited retakes of the Quant Readiness Diagnostic.

To keep the material accurate and current, we may add, revise, reorder or retire individual lessons, labs, notebooks and questions. If a change materially reduces what Premium includes during a period you have already paid for, tell us within 30 days and we will refund the unused part of that period.

We may give some people complimentary Premium access for a fixed period, for example beta testers. It costs nothing, ends automatically on the date we tell you, and never turns into a paid subscription unless you subscribe yourself.

• Premium is sold as a monthly or an annual subscription. The price and billing period are shown on the Pricing page, and again at checkout before you pay.
• Prices are in US dollars. The amount shown at checkout is the total you pay for each billing period, including any tax we are required to collect. Your card issuer may add its own foreign-transaction or currency-conversion fees.
• Payments are processed by Stripe. We never receive or store your full card details.
• Your subscription renews automatically at the end of each billing period, charging the then-current price to your saved payment method, until you cancel.
• If a renewal payment fails, Stripe retries it over the following days and your Premium access continues while it does. If the payment still cannot be collected, your subscription may be cancelled and Premium access stops.
• If we change the price, we will email you at least 30 days before it applies. The new price applies from your first renewal after that notice, and you can cancel before then.

• You can cancel at any time from your dashboard (“Manage subscription”) or by emailing us. Cancelling stops future renewals, and you keep Premium until the end of the period you have paid for.
• 14-day money-back guarantee. If you ask within 14 days of the first payment for a new subscription, or within 14 days of an annual renewal payment, we will refund that payment in full.
• Monthly renewal payments are not otherwise refunded.

The full details, including how to ask for a refund, are in our Refund & Cancellation Policy. Nothing in it or in these terms affects your legal rights as a consumer.

You agree not to:

• copy, bulk-download, scrape, republish, sell or otherwise redistribute content from the Service, including lessons, notebooks, code, quiz questions and worked solutions;
• share, publish or sell questions or answers from the Quant Readiness Diagnostic or the quizzes;
• use content from the Service to train or fine-tune machine-learning models;
• get around paywalls, rate limits or other access controls, or probe, scan or test the security of the Service without our written permission;
• use scripts, bots or other automation to complete modules, submit quizzes or otherwise gain XP or leaderboard position;
• impersonate anyone, choose a handle or display name that is offensive or infringes someone else’s rights, or use the Service unlawfully.

XP, levels and leaderboard positions have no monetary value and cannot be transferred. We may correct or remove them if they were gained through a bug, an error or a breach of these terms.

The Service and its content belong to us or our licensors. That includes course text and derivations, interactive labs, notebooks, source code, quizzes, the Quant Readiness Diagnostic, and the Brownian Bridge name and logo.

While your account is in good standing, we give you a personal, non-exclusive, non-transferable licence to use the content for your own learning. You may adapt short code examples in your own non-commercial learning projects. Any other use needs our written permission.

Every account has a public profile page and can appear on the public leaderboard. Both show your handle, your display name if you set one, your level, your total XP, the number of modules you have completed, the number of quizzes you have taken, and the month you joined.

When you sign up you get a random handle. You can change your handle and display name at any time under Dashboard → Profile. Accounts created before 17 September 2026 may have a handle based on their email address, which can be changed in the same place.

The Service is educational. Nothing on it is financial, investment, tax, legal or career advice, or a recommendation to buy or sell any financial instrument. Models, prices and code are illustrations for learning. Do not use them for trading, risk or investment decisions without your own independent validation.

Quant Readiness Diagnostic results, levels and XP indicate your own progress. They are not a qualification or certification, and we do not guarantee any interview, job offer or other career outcome.

We work hard to make the material correct, but it may contain errors. If you find one, please tell us.

We aim to keep the Service available and working, but it may occasionally be unavailable for maintenance, updates or reasons outside our control.

We may change the Service or stop providing it. If we stop providing Premium, we will give you at least 30 days’ notice where we reasonably can, and refund any payment covering a period you will not receive.

If you are a consumer

We are responsible for loss or damage you suffer that is a foreseeable result of our breaking these terms or failing to use reasonable care and skill. Loss or damage is foreseeable if it is obvious that it will happen, or if both of us knew it might happen when the contract was made. We are not responsible for loss or damage that is not foreseeable.

If defective digital content we have supplied damages a device or digital content belonging to you, we will either repair the damage or pay you compensation. We are not liable for damage you could have avoided by following our reasonable advice.

The Service is for domestic and private use. If you use it for a commercial or business purpose, we have no liability to you for loss of profit, loss of business, business interruption or loss of business opportunity.

If you are a business customer

We are not liable for indirect or consequential loss, or for loss of profits, revenue, business, goodwill or data. Our total liability to you in connection with the Service is limited to the fees you paid us in the 12 months before the event giving rise to the claim.

For everyone

Nothing in these terms limits or excludes our liability for death or personal injury caused by our negligence, for fraud or fraudulent misrepresentation, or for anything else that cannot be limited or excluded by law. That includes your statutory rights as a consumer.

You can ask us to close your account at any time by emailing us from the address on the account. If you have an active subscription, we will cancel it at the same time. What happens to your data is explained in our Privacy Policy.

We may suspend or close your account if you seriously or repeatedly break these terms, for example by sharing your account or redistributing content, and we will tell you why. If we close your account for any other reason, we will refund any payment covering a period you will not receive.

We may update these terms, for example to reflect changes in the law or in the Service. If a change materially affects you, we will email you at least 30 days before it takes effect. For a paid subscription, the new terms apply from your first renewal after that notice. If you do not agree, you can cancel before then.

These terms are governed by the law of England and Wales. If you are a consumer, you can bring proceedings in the courts of England and Wales, or in Scotland or Northern Ireland if you live there. If you live elsewhere, you keep the protection of the mandatory consumer laws of your country of residence, and nothing in these terms removes any right you have to bring proceedings in your local courts.

If you have a complaint, please email us first. Most issues can be resolved quickly.

If a court finds any part of these terms unenforceable, the rest stays in effect. You may not transfer your rights under these terms to anyone else. We may transfer ours to someone who takes over the Service. We will tell you if we do, and it will not reduce your rights as a consumer.

Benoit Vandevelde, trading as Brownian Bridge
Flat 204 Hampton Apartments, Duke of Wellington Avenue, London SE18 6NX, United Kingdom

Email: contact@brownian-bridge.com