Pick a time control and press Start game. Tap the other player’s face to start their clock, or, in Clock + scoresheet, tap a piece and then its square and the clock presses itself. Two sample games are in the history so there is something to review. On a wide screen, open it in a full window and the board sits beside the clock. The vibration setting is there and does nothing in a browser. It is the app that is on the App Store and Google Play, built from the same code, not a cut-down version, with every time control and the scoresheet.
What this page does and does not do
- Your games stay in this browser. Finished games, your own time controls and settings are kept in this browser’s storage, not in an account. They do not follow you to another browser, another computer or your phone, and clearing your site data or using a private window loses them.
- There are no ads here. The ad network has no browser version, so there is nothing to show. The phone app is different: it carries a banner on the home screen, in history, in review and in Settings, never on the running clock.
- Nothing is sold, and no game you play is sent anywhere. No in-app purchases, no account and no sign-in. This build has no analytics, no crash reporting and no advertising in it. The phone app’s, described in its privacy policy, are left out of the browser version. In a session measured against it, no request left this domain, fonts and sounds included. It sets no cookies of its own. This page does carry the same analytics as every other page on the site, which is described in the privacy policy; in the EEA, the UK and Switzerland it stays off until you accept the banner.
- Nothing comes from Google, fonts included. The rendering engine is served from this domain, not from Google’s CDN. That is not the framework default; we changed it on purpose. The typefaces, Barlow and Roboto, are bundled with the app and served from here too, so the browser asked no other domain for anything. Checked against this build on 28 October 2026, starting a game and making a move. A screen we did not open could still ask Google for a symbol those fonts lack.
If it runs badly
It is a little under three megabytes the first time in Chrome and about three and a half in Safari, most of it the rendering engine rather than the clock. Those figures are this build’s own files compressed locally on 28 October 2026 rather than a reading taken off the wire, so what Cloudflare actually serves may differ a little. It also leans on the browser rather than the phone’s graphics chip, so an old laptop or a weak connection will feel it, and the first load is slower than the second because nothing is cached yet. The installed app has neither problem. What Chess Clock costs and what it collects are on its own page.