quirksmode.org

What It Is

QuirksMode.org is the personal website of Dutch front-end developer and browser researcher Peter-Paul Koch (ppk). From 1999 to 2014, it played a role somewhat like “MDN + Can I use,” documenting compatibility differences across browsers in JavaScript, CSS, DOM, the mobile Web, and more. Today, the site is more of a combination of historical archive, personal blog, and entry point for conferences, books, and consulting.

Core Features

The site’s core value lies in preserving old browser compatibility tables and browser quirks documentation, making it useful for troubleshooting legacy system issues or studying differences in early Web behavior. In addition, QuirksBlog offers the author’s long-running observations on front-end development, and the site links to conferences such as CSS Day and performance.now(), as well as the author’s books, including ppk on JavaScript, The Mobile Web Handbook, and a handbook on conference organization.

Pricing

Based on the crawled content, QuirksMode.org does not appear to have a clear paywall or subscription pricing, and its main content is freely accessible. The author has mentioned maintaining the site unpaid for many years and eventually stopping large-scale browser research due to lack of funding and burnout. He has also expressed interest in Web Monetization, but no specific commercial plans or packages are currently visible.

Pros and Cons

Its strengths are its authority and historical value. The author is a well-known figure in the front-end community, and the site’s materials influenced a generation of developers. For old browser issues, it may still be more targeted than modern documentation. The drawbacks are also clear: its core compatibility research largely stopped around 2014/2015, so coverage of modern browsers and modern CSS/JS APIs is limited. The site also has a more traditional structure, with search and structured browsing experiences that are not as polished as MDN, Can I use, or web.dev.

Who It’s For

It is suitable for front-end engineers maintaining older Web projects, browser compatibility researchers, enthusiasts of Web standards history, and people interested in Peter-Paul Koch’s consulting, training, and conference-organizing experience. It is not recommended as the sole compatibility reference for modern front-end development.

Access from China

Judging by the nature of the site and its domain, it is a standard technical resource website and can usually be accessed directly. If some resources fail to load, it is more likely due to external links or network fluctuations rather than restrictions imposed by the site itself.