Frequently Asked Questions

D4 Chess Club™ (d4chess.club) is a web-based chess training platform built specifically for club players — typically rated between 800 and 2000. It combines Stockfish engine analysis, an AI coaching system, tactical puzzle practice, opening recognition, and structured courses into one free-to-start app. Unlike general chess platforms, D4Chess focuses on training you to improve, not just to play games. It is designed for players who are serious about getting better but do not have access to a human coach.

Yes. D4 Chess Club™ has a permanent free plan that includes playing against a computer opponent (adjustable from 1000 to 3200 Elo), full Stockfish game analysis with move classifications, a real-time threat overlay, puzzle practice (5 puzzles per day), the Chess Basics course, and access to the leaderboard. No credit card is required to sign up. The free plan also includes three AI coaching sessions per month. A premium plan at $5.99 per month unlocks unlimited coaching sessions, advanced courses, and unlimited puzzles.

The D4Chess AI coach uses the Socratic method: instead of immediately telling you the best move, it asks targeted questions that guide you to find the answer yourself. After you play a game or import one, the coach walks through your moves one by one, explains what went wrong, identifies the pattern behind the mistake (hanging pieces, missed forks, king safety errors, etc.), and asks you to reason through the position. This approach builds lasting pattern recognition rather than passive memorization. Every coaching explanation is grounded in verified engine analysis so the coach never gives you incorrect assessments of a position.

Regular Stockfish analysis in D4Chess classifies every move as book, best, good, inaccuracy, mistake, or blunder and shows the engine's top continuation. The AI Walkthrough goes a level deeper: it selects your key moments (including excellent moves, not just mistakes), fetches a personalized explanation for each one from the coaching AI, shows you the punishment line your opponent could have played, and lets you explore Stockfish's best continuation from any position. You can also ask the coach follow-up questions in natural language during the walkthrough. Regular analysis is available on the free plan; the full AI Walkthrough requires a premium subscription.

Chess.com and Lichess are primarily playing platforms — their analysis tools are extensive but general-purpose. D4Chess is built around a single goal: helping club players find and fix their specific weaknesses. The AI coach identifies recurring patterns across your game history (not just one game), asks Socratic questions to build reasoning skills, and recommends drills targeting exactly those patterns. D4Chess also offers a real-time threat overlay during game review, which visually highlights attacks, hanging pieces, and king danger on the board as you step through moves. Chess.com and Lichess do not offer this style of targeted coaching.

Yes. D4Chess supports three import methods. You can paste a PGN (Portable Game Notation) string directly into the analyzer — any game exported from Chess.com, Lichess, or a tournament database works. You can also upload a PGN file. Additionally, D4Chess has a Board Scanner feature that lets you photograph a physical chessboard or a position from a book, converts the image to a FEN, and opens that single position for Stockfish exploration or a coach session (full move-by-move game review still needs a PGN). Lichess and Chess.com username import (pulling your recent games automatically) is available through the import panel.

D4Chess runs Stockfish 18 — the strongest open-source chess engine in the world — on the backend to analyze every position in your game. For each move, the engine calculates the centipawn evaluation before and after the move, identifies the best move available, and computes a principal variation (the best continuation for both sides). D4Chess uses the centipawn loss to classify each move: 0–5 cp loss is 'best,' 5–20 is 'good,' 20–60 is 'inaccuracy,' 60–150 is 'mistake,' and 150+ is 'blunder.' After full game analysis, D4Chess calculates an accuracy percentage for each player using a formula that matches industry standards.

The free plan includes: play vs computer (1000–3200 Elo), Stockfish game analysis, real-time threat overlay, puzzle practice (5 puzzles per day), the Chess Basics course, and 3 AI coaching sessions per month. The premium plan ($5.99/month) adds: unlimited AI coaching sessions, the full AI Walkthrough in post-game review, the Tactics 101 course (23 lessons), the Opening Principles course (10 lessons, 30 grandmaster games), unlimited puzzles, and access to all future courses. Both plans include the same Stockfish analysis depth — premium does not give you stronger engine analysis, just more coaching and learning content.

Every game you play or analyze in D4Chess is tagged by move type and mistake pattern — hanging pieces, missed forks, back-rank mate threats, king safety errors, opening principle violations, and more. The AI coach reads these tags when explaining a mistake and connects them to recommended puzzle drills. Over multiple games, the pattern of which mistake types appear most often defines your 'weakness profile.' The Recommended Drills section at the end of each game review reflects this — it routes you to puzzle themes and drill types that match the mistakes you actually made, not generic tactics everyone does.

Yes. D4Chess includes opening recognition in its analysis engine — it identifies the opening name (with ECO code) for any position in your game, up to and including less common lines like the Cow Opening, the Bull Opening, the Sveshnikov Sicilian, and hundreds of others. The Openings section in the app lets you study theory. The Opening Principles course (premium) teaches the 10 core principles behind opening play using 30 annotated grandmaster games. A full opening repertoire builder (where you drill your personal opening lines) is on the development roadmap.

D4Chess includes hundreds of tactical puzzles covering all major themes: forks, pins, skewers, discovered attacks, back-rank mates, king safety, and endgame technique. Free users get 5 puzzles per day; premium users get unlimited access. Puzzles are categorized by theme so the drill recommendation system can route you to the specific pattern types your games reveal as weak spots. Puzzles also integrate with a rating system that adjusts difficulty to your solving history, and spaced repetition scheduling (SM-2 algorithm) is on the roadmap to review puzzles at optimal intervals.

D4Chess is designed primarily for club players — roughly 800 to 2000 Elo on Chess.com or USCF. The adjustable computer opponent covers 1000 to 3200 Elo, so absolute beginners and advanced players can both find a suitable sparring partner. The AI coaching is most effective in the 1000–1800 range where tactical mistakes are frequent and identifiable. Very strong players (above 2000) will find the analysis and puzzles useful, but the coaching explanations are written for club-level understanding rather than master-level subtlety.

D4Chess is a progressive web app (PWA), which means you can install it to your iPhone or Android home screen directly from the browser — no app store required. On iOS, open d4chess.club in Safari, tap the Share button, and choose 'Add to Home Screen.' On Android, open it in Chrome and tap 'Add to Home Screen' in the browser menu. The installed PWA runs full-screen, works offline for certain features, and behaves like a native app. A dedicated iOS and Android app is on the development roadmap.

Yes — stopping blunders is the core use case D4Chess is built for. The most common reason club players blunder is that they fail to see their opponent's threats. D4Chess addresses this directly with a real-time threat overlay that renders attacks, hanging pieces, and king danger on the board during game review. The AI coach then explains why each blunder happened (what threat was missed, what tactical pattern was overlooked) and recommends drills for that specific pattern. Players who use D4Chess consistently for 30 days typically see measurable reductions in blunder rate as pattern recognition improves.

D4Chess uses Stockfish 18 at a consistent analysis depth tuned for fast, accurate results across every move in a game. Stockfish is rated approximately 3500–3600 Elo — far above any human player — making its evaluations effectively definitive at club level. The centipawn evaluations, move classifications, and best-move suggestions in D4Chess are based directly on Stockfish output with no modification. Move classification thresholds (inaccuracy, mistake, blunder) follow widely accepted standards used by other major chess platforms.

Navigate to the Analyzer section in D4Chess (from the sidebar or mobile menu). Paste your PGN or upload a PGN file — you can export a PGN from any game on Chess.com, Lichess, or any tournament software. Click 'Analyze Game' and D4Chess runs Stockfish on every move, typically taking 30–60 seconds for a full game. Once complete, you see accuracy scores for both players, a breakdown of blunders/mistakes/inaccuracies, move-by-move classifications with the engine's best continuation, and drill recommendations. Premium users can then launch the AI Walkthrough to get coaching explanations for each key move.

D4Chess Premium costs $5.99 per month. It includes unlimited AI coaching sessions (the free plan gives 3 per month), the full AI Walkthrough in post-game review, the Tactics 101 course (23 lessons covering forks, pins, skewers, and discovered attacks taught from grandmaster games), the Opening Principles course (10 principles, 30 grandmaster games), and unlimited puzzle access. There is no annual plan currently — the subscription renews monthly. The price may change as new features are added, but existing subscribers are grandfathered at the rate they signed up at.

Yes. D4Chess Premium comes with a 7-day money-back guarantee. If you upgrade and decide within 7 days that premium is not right for you, you can request a full refund. After 7 days, the subscription is non-refundable but you can cancel at any time and retain access until the end of the billing period. To request a refund or cancel, use the profile page inside the app or contact support.

You can cancel D4Chess Premium from your profile page inside the app — click your username in the top right corner, go to Profile, and find the subscription management section. Cancelling stops the next billing cycle; your premium access continues until the end of the current paid period. You will not lose your game history, analysis data, or progress when you cancel — everything is saved to your account. If you resubscribe later, all your history is still there.

Some D4Chess features work offline after the app has been installed as a PWA. The chessboard and game navigation work offline. Stockfish analysis, AI coaching, online puzzle fetching, and importing from Chess.com or Lichess require an internet connection because they call the D4Chess backend. For offline analysis, the Stockfish engine runs on the D4Chess server rather than in the browser, which delivers stronger analysis than browser-based engines but does require connectivity.

D4Chess is built and operated by Haven Command LLC, an independent software company focused on AI-powered tools for skill development. Haven Command LLC also operates other products in the training and productivity space. D4Chess is available at d4chess.club. For business inquiries, visit havencommand.com.