Lichess on any website.

Lichess.org launched in 2010 as a side project by Thibault Duplessis. By 2017 it had grown big enough to register as a French non-profit (association loi 1901), and it has operated under that structure ever since. Every line of code on Lichess.org is published openly under the AGPL license, which means anyone can read, audit, fork or self-host the entire platform. There has never been a paid tier. There have never been ads. Server costs and a tiny core team are funded entirely by community donations, with full financial transparency published on the site. The contrast with the commercial chess industry is stark: Chess.com is a for-profit company with a tiered subscription model, premium puzzles paywalled behind paid plans, and ads on free accounts. ChessKid, the kids product, is also paid. Decode Chess, ICCF and most engine analysis tools are commercial. Lichess offers everything those products charge for at no cost, with the same or better quality, and publishes the source code so you can verify it. When you embed a Lichess widget on your site, you are not just showing a profile, you are aligning yourself with that open-source ethos.

Lichess maintains separate Glicko-2 ratings for five standard time controls (Classical, Rapid, Blitz, Bullet and UltraBullet), plus separate ratings for every chess variant the platform supports: Atomic, Crazyhouse, Chess960, King of the Hill, Antichess, Horde, Three-check and Racing Kings. That granularity matters because chess strength is not a single number. A 2400 Bullet specialist might be 2000 Classical. A serious Crazyhouse player might be the world top-100 in that variant and only club-level in standard chess. A widget that only shows one rating misses most of the picture. Poper's ratings block exposes a switchable tab so visitors can see Classical, Rapid, Blitz, Bullet and UltraBullet on demand, plus an optional variants drawer for the Lichess-only formats. Coaches use this to demonstrate format range, club leaderboards use it to sort members by their preferred control, and variant specialists finally have a way to surface the rating that actually represents what they play.

Lichess Studies are the platform's killer feature for serious chess work. A Study is a shareable, chaptered analysis document with full board annotation, multiple variations, embedded videos, computer evaluation and collaborative editing. Coaches publish opening repertoires and endgame trainers as Studies. The Lichess team and World Champion-level commentators publish annotated master games as Studies. Universities run their tournament prep as Studies. Chess.com has no real equivalent (their lessons product is paywalled, single-author and not shareable in the same way). Poper's widget treats Studies as first-class content: you can mirror your public Lichess Studies on your own site with chapter counts and direct links, so prospective students see exactly the training material you teach with before booking a lesson. Puzzles are similar. Lichess publishes its full puzzle database under an open license, runs Puzzle Rush and Puzzle Storm modes free for everyone, and surfaces a Glicko-rated Puzzle rating per account that you can show alongside your standard ratings to demonstrate tactical strength.

Lichess publishes its source code under AGPL, but the widget you embed on your site is also code that runs in your visitors' browsers. That code matters. Image-heavy chess widgets (boards, piece sprites, game replay) are notorious Core Web Vitals killers when they are written carelessly. The worst offenders load 200KB+ of JavaScript synchronously, fetch the full Lichess profile on every single page view instead of caching, and inject styles that override your design system. The result is a hit to your Largest Contentful Paint, your Cumulative Layout Shift, and your overall Lighthouse score, exactly the metrics Google now uses as a ranking signal. Poper's Lichess widget loads asynchronously below the fold by default, fetches profile data from a global CDN edge cache (so your visitors do not hit Lichess.org on every page view, which also respects the platform's published rate limits), uses scoped CSS that will not bleed into your design system, and clocks in under 40KB gzipped. If page speed matters to your SEO, this is the single biggest reason to choose carefully which Lichess widget you embed.

Both Chess.com and Lichess have legitimate reasons to be on a chess content creator's site. Chess.com is the largest commercial chess platform, has the strongest streamer roster, and runs the highest-prize-money online events. Lichess is the open-source, ad-free, donation-funded alternative that owns the FOSS, academic and serious competitive variants communities. Many serious players have accounts on both. The decision tree is simple: if your audience cares about the open-source ethos, if you teach with Lichess Studies, if you compete in Lichess Arenas, if you play variants, or if you simply prefer a platform with no ads and no upsells, embed your Lichess feed. If your primary chess content is on Chess.com (Twitch streams, Chess.com events, paid lessons there), embed the Chess.com widget instead. There is also nothing stopping you from embedding both, side by side, on a single chess content page. Poper supports both widgets natively and you can configure them in the same dashboard.