Privacy

algos.sh is a free site for learning algorithms and practising for coding interviews. It has no ads and no third-party trackers. It keeps only what it needs to save your progress and to count visits, and you can delete your progress whenever you like.

The short version

• Reading the guides sets no cookies and stores nothing about you.
• Practice pages (problems, quizzes, the roadmap) set one cookie so your progress is saved, first as a guest, later under your GitHub account if you sign in.
• We store the code you run and your answers, to show your progress and schedule reviews.
• We count page views with our own cookie-free counter, which can't tell who you are.
• No advertising, no third-party analytics, no selling or sharing your data.
• You can delete everything from your progress page. Guest progress that goes unused for 90 days is deleted automatically.

Cookies and browser storage

Guide pages set no cookies. Practice pages set a single cookie, _algos, which holds a signed identifier for your guest or signed-in account and a security token that protects your answers from being forged by other sites. It's needed for the site to work, so there's no banner asking about it. It lasts a year.

Your browser's local storage keeps a few conveniences on your device only: the programming language you last picked, and unsaved drafts of your code so a reload doesn't lose them. We never see these.

What we store

• Your account: a random ID, when you were last active, and your browser's time-zone offset (so streaks follow your local day). If you sign in with GitHub: your GitHub user ID, username, display name and avatar URL. We ask GitHub only for your public profile, never your email, repositories or anything else.
• Practice: the code you run or submit, which language, how many levels passed, how long you took, whether you opened the solution, and the rating you give. Your quiz, "which technique?", math and puzzle answers, and your mock-assessment sessions.
• Derived data: review schedules, streaks and a mastery score per topic, computed from the above.

We don't collect your name (beyond GitHub's), email address, location or payment details. There is no advertising or third-party analytics code on the site.

Counting visits

To know which pages are useful, each page you open sends one small request to our own server with the page's address and, on the first page of a visit, the website that linked you here (just its name, like google.com). We add these up into daily totals: views per page, links per referring site, and the number of distinct visitors that day.

To count distinct visitors without cookies, the server combines your IP address and browser type with a random value that is replaced every day, and keeps only a scrambled result, in memory, for that day. Nothing about you is written to disk: we store only the totals, so we can't tell who visited or follow you from one day to the next. If your browser sends "Do Not Track" or "Global Privacy Control", pages don't send this request at all.

The code you run

When you press Run or Submit, your code is sent to our server and executed in a throwaway, locked-down container with no network access. The container and its files are deleted as soon as the run finishes. A copy of the code is kept with your attempt so you can come back to it. Please don't put personal or confidential information in your code.

Other services involved

• Cloudflare sits in front of the site, like most sites, to deliver pages quickly and block attacks. It handles your requests, including your IP address.
• jsDelivr serves MathJax, the library that draws math formulas, on the pages that contain math. Your browser fetches it directly, so jsDelivr sees that request.
• GitHub, only if you choose to sign in with it.

Our server, run by us, keeps the data above. Standard server logs (requests and errors) are kept briefly for keeping the site running and aren't used for anything else.

Why we use it

Only to run the site for you: saving and showing your progress, scheduling re-solves, finding your weak spots, and keeping the code runner safe from abuse (for example, limiting how often any one account or network address can run code). For those limits your IP address is counted in memory for up to an hour; it isn't saved with your account.

Your control

• Delete everything: the "Delete all my data" button on your progress page removes your account and every attempt and answer, immediately and permanently.
• Guests: clearing your cookies starts you fresh. The old guest progress is deleted automatically after 90 days without activity.
• Anything else, including a copy of your data: email [email protected].

Children

The site is meant for people preparing for technical interviews and isn't directed at children under 13.

Changes

If this changes in a way that matters, for example if we add paid plans or new services, we'll update this page and the date at the top.