How CodeYouKnow handles your data
Last updated 2026-10-13.
Who runs this site
CodeYouKnow (codeyouknow.com) is run by Denis Liamkin as a personal project. For anything about this policy or your data, email [email protected].
This page describes what the site collects, why, who else handles it, and how to get it changed or deleted. It is written in plain language on purpose.
Practicing without an account
You can use every exercise and the daily regex puzzle without signing in. Your progress then lives only in your browser's local storage: which exercises you solved, the code you wrote, which exercise is open, your theme, and your daily puzzle attempts and record. None of it is sent to us until you sign in, and clearing your browser data removes it.
What an account stores
Signing in uses Google or GitHub. We never see your password. From the provider we receive and keep:
- An account id, your email address, the name on the account and its avatar picture.
- A handle, generated from your provider username or email, which you can change.
- Anything you add on your account page: a display name and a short bio.
Your account then holds your practice data so it follows you between devices: the exercises you solved and the code that passed, your drafts, your settings, the variations generated for you, and your daily puzzle attempts.
Your profile is private unless you switch it to public on your account page. A public profile shows your handle, display name, avatar, bio, solved counts and activity calendar at codeyouknow.com/u/your-handle, and nothing else.
Code reviews and variations (Anthropic)
"Review my code" and "New variation" are built on Claude, a model made by Anthropic. When you use them, the exercise, your code and your test results are sent to Anthropic's API to produce the answer. Nothing about who you are travels with them.
Under Anthropic's commercial terms, data sent through its API is not used to train its models. We keep a record of each call (which exercise, when, how many tokens, what it cost) to enforce allowances and watch our spend. Generated variations are stored with your account, and a validated one may be shown to other people practicing the same exercise, without your name.
Running your code
JavaScript, TypeScript, Python, SQL, Angular, RxJS, React and Vue run entirely in your browser; your code never leaves it for a test run.
Rust, C# and Java are compiled and run on third-party services, Compiler Explorer (godbolt.org) and the Rust Playground (play.rust-lang.org), through our server. Only the program itself is sent, built from your code and the exercise's tests; no account details go with it. Each service has its own privacy policy.
Payments (Polar)
Pro and credit packs are sold through Polar, our merchant of record. Polar takes the payment, applies any tax your country requires and sends the receipt. Your card details go to Polar and its payment processor, never to us.
Polar tells our server about each order and subscription change so your account can be updated. We keep those records, which include the name, email and billing details you entered at checkout, for as long as accounting rules require. You can see and manage your subscription, invoices and card through "Manage billing" on your account page, which opens Polar's customer portal.
We send one welcome email when you create an account, through Resend. Any other email, for example a note when a new language lands, is sent only if you opt in on your account page, about once a month at most, and you can switch it off there at any time. Mail you send to [email protected] is received through Cloudflare Email Routing and read by Denis.
Analytics and cookies
We use Google Analytics 4 to see which pages are visited and whether the site works. It receives:
- Page views, with the page's address.
- A few events: signing up, signing in, the first exercise solved, the first code review, and sharing a puzzle result, each with the language or method involved and nothing more.
Google Analytics sets its own cookies and shortens IP addresses before storing anything. The Google sign-in button on the sign-in dialog is loaded from Google and may set cookies of its own. Fonts are loaded from Google Fonts, which sees your IP address when the page loads. We show no ads and use no ad networks.
Your sign-in session and your practice data are kept in your browser's local storage, not in cookies.
Hosting and technical logs
The site and its API run on Cloudflare; the database and sign-in run on Supabase. Cloudflare keeps short-lived request logs (IP address, address requested, timing, errors) for security and debugging, and limits how often one address can call the API. Supabase stores the account and practice data described above.
How long we keep things
- Account and practice data: as long as the account exists.
- Records of AI calls and billing events: as long as accounting and abuse prevention require, then deleted or reduced to totals.
- Technical logs: days.
- Local storage in your browser: until you clear it or sign out, which removes the practice keys from that device.
Your choices and rights
- See or export your data: email us and we send you a copy.
- Correct it: display name, handle, bio and the email opt-in are on your account page.
- Delete it: email us from the account's address and we delete the account and everything linked to it within 30 days. Polar keeps the invoices it issued, as it must.
- Analytics: block or clear cookies in your browser, or use Google's opt-out add-on; the site works the same.
If you are in the EU, the UK or another place with data protection law, these are the rights those laws give you (access, correction, deletion, objection, portability), and you can also complain to your local authority. We do not sell personal data and never have.
Children
CodeYouKnow is not meant for children under 16, and we do not knowingly keep an account for one. If you believe a child has signed up, email us and we delete it.
Changes to this policy
When a data practice changes, this page changes with it and the date at the top moves. A change that matters, such as a new third party receiving your data, is announced to accounts that opted in to email.