Terms of use

Last updated 10 August 2026.

By using theopeningclub.com you accept these terms. They are short because the site is simple: it publishes chess opening statistics and writing about them, free, with no account required. The site is operated by Ground Plane Studio, LLC, of San Francisco, California, referred to below as we and us.

What the statistics are

Every figure on this site describes what happened in a large set of recorded games, at a stated rating band, with its sample size shown. That is a description of a population, not a prediction about you. An opening graded S at 1000 will still lose games, including yours, and a D grade has beaten stronger players than either of us. Nothing here is a guarantee of a result, a rating gain, or an improvement in your play.

Two limits are worth stating plainly rather than burying. The blunder rate is a material-swing proxy computed without an engine, so it measures how sharp a position tends to be in practice and not whether a specific move was an error. And per-opening figures are only as good as their sample size, which is why every one of them is printed next to its n. The method page gives the full formulas.

Corrections

If a number here is wrong, we want to know and we will fix it. Every figure is reproducible from the source data, so a report naming the page and the rating band is usually enough to settle it either way. Write to hello@theopeningclub.com.

Where the data comes from

Statistics are computed from the Lichess open database, released under CC0. Lichess is a separate organisation, is not affiliated with this site, and does not endorse it. We are grateful for the database and say so on every page that uses it.

Using our content

The editorial writing, the tier grades, the rankings and the way the figures are presented are the property of Ground Plane Studio, LLC. You are welcome to quote a figure or a passage with attribution and a link back to the page it came from, and you do not need to ask. Republishing whole articles, or scraping the site to rebuild the dataset elsewhere, is not permitted. The underlying game data is CC0 and always was, so if you want the raw material, take it from Lichess directly rather than from us.

Acceptable use

Read the site, use the tools, link to anything. Do not attempt to break it, overload it with automated requests, or use it to distribute anything unlawful. Automated bulk crawling that degrades the site for other readers may be blocked.

Affiliate links

Some outbound links earn us a commission, marked as such and described in full on the affiliate disclosure page. They do not affect any statistic, grade or ranking on this site, and no partner has ever been offered the chance to influence one.

Third-party sites

Links to Lichess, Chess.com, Chessable and elsewhere are for your convenience. Those sites have their own terms and privacy policies and we are not responsible for what they do.

Availability and warranties

The site is provided as is. We make no warranty that it will be available without interruption, that it will be free of errors, or that it is fit for any particular purpose. Data pipelines run monthly and can fall behind; when a figure is stale or missing, the page says so rather than guessing.

Limitation of liability

To the fullest extent the law allows, Ground Plane Studio, LLC is not liable for any indirect, incidental or consequential loss arising from your use of the site. Nothing in these terms limits liability for fraud, or for anything else that cannot lawfully be limited.

Governing law

These terms are governed by the laws of the State of California, without regard to its conflict of law rules, and the state and federal courts located in San Francisco County, California have exclusive jurisdiction over any dispute arising from them.

Changes

These terms may change. The date at the top changes with them, and continuing to use the site after a change means you accept the revised version.