Privacy

Short version: Best Sudoku doesn’t ask who you are and doesn’t show ads. The only cookies are Google Analytics cookies, which help us see how the site is used.

What stays on your device

Your progress, settings, streak and stats are saved in your browser’s local storage on your device. Clearing your browser’s site data removes them. Nothing is sent anywhere for this.

Optional sync

If you turn on sync in Settings, a copy of your progress (streak, stats, XP, achievements and daily results, but not in-progress boards or settings) is stored on our server. It is filed under a one-way hash of your sync key. We never store the key itself, so we can’t tell whose progress is whose, and we can’t recover a lost key. Anyone who has your key can read and change that copy, so keep it private. You can stop syncing at any time in Settings.

Analytics

We use Google Analytics to count page views and simple events, such as a puzzle being started or finished, so we can see what works. Google Analytics sets cookies (named _ga) and receives your IP address and basic device and browser details. Google explains how it uses this data at policies.google.com/technologies/partner-sites. You can opt out with Google’s browser add-on at tools.google.com/dlpage/gaoptout, or by blocking cookies for this site.

We may also use Plausible Analytics, which doesn’t use cookies or collect personal data.

Hosting and fonts

The site is hosted on Netlify, which keeps standard server logs, such as IP addresses, for security and operations. Fonts are served from this site, not from a third party.

No ads, no selling

There are no ads, and we don’t sell your data. Apart from the Google Analytics described above, there are no third-party trackers.

Changes

If this policy changes, this page will show the new version. Last updated October 2026.