Privacy

Your progress — which levels you cleared, your answers, your XP, your theme and the settings you chose during onboarding — is written to your browser's localStorage under keys beginning ytyk/. It never leaves your device, and nobody but you can read it. Clearing your browser's site data for ytyk.org erases it permanently; there is no copy anywhere to restore from.

This also means your progress does not follow you to another browser or another machine. That is the trade for not asking you to sign up.

The site uses Umami for analytics. It does not set cookies, does not follow you across sites, and does not build a profile of you. What it records for each page view is the page's address, the referring site if there was one, and — derived from your IP address rather than stored with it — your approximate country, browser, operating system and screen size.

Your answers, your progress and anything you type into a sandbox are never sent to it, or anywhere else. The analytics data is processed by Umami Software, Inc. on our behalf; if you would rather not appear in it at all, any content blocker that blocks cloud.umami.is will do it, and the site works exactly the same with it blocked.

Three other parties receive a request from your browser in normal use:

• GitHub Pages and Cloudflare serve the site, so they see the requests for its pages and files, including your IP address, as any web host does.
• jsDelivr or unpkg — only in the Python course, and only the first time you press Run. That is when the Python interpreter itself (around 10 MB) is downloaded to your browser and cached.
• cdnjs or jsDelivr — the same, for SQLite in the SQL course, the first time you press Run there.

Nothing you write is sent to any of them: your code runs inside your own browser, which is the whole point of the design. If you never press Run, no CDN is ever contacted.

The home page carries a newsletter sign-up form. The form itself is part of this page and costs nothing to show; the scripts that make it work come from Infomaniak (newsletter.infomaniak.com) and are fetched only when you click into the field. If you never do — which is almost everyone — your browser never contacts them at all.

There are no web fonts, no embedded video and no advertising.

The sign-up is run by Infomaniak, a Swiss company, on servers in Switzerland. The form is written into this page, so showing it contacts nobody. Touching it fetches two things from newsletter.infomaniak.com — their submit handler, and Altcha, a spam check that has your browser solve a small puzzle instead of asking you to identify traffic lights, and which sets nothing and follows nobody. From that point Infomaniak can see your IP address, as any host you fetch from can.

Submitting sends your email address to them and nothing else — this page knows nothing about you to send. You will then get a confirmation link, and you are not subscribed until you click it, so an address typed in by somebody else never becomes a subscription. The mail is delivered through Amazon SES, so your address passes through Amazon Web Services on its way to you.

Your address is used for these announcements and for nothing else: not advertising, not sold, not shared beyond the delivery chain above. Every message carries an unsubscribe link that works immediately, and you can ask us to delete your address at any time at [email protected]. Blocking newsletter.infomaniak.com costs you only the form.

Subscribing is entirely optional, and nothing about the site changes if you do not. Your progress and your answers are never connected to your email address, because they never leave your browser in the first place.

Because there are no accounts, most of what you might ask for is already in your hands: you can inspect your stored progress in your browser's developer tools and delete it by clearing site data. The analytics data is aggregate and not linked to you, so there is nothing there to look up, correct or export on request.

If you are in the EU or the UK: the legal basis for the analytics is legitimate interest in knowing whether the site is used, and the data is neither personal enough nor retained in a form that could identify you. For anything else — a question, a correction, a request — write to [email protected].

If this notice changes, the date at the top changes with it. The site's history is public, so every previous version of this page is in the repository's commit log.