How accurate is Stockfish compared to human players and other engines?

Stockfish is much stronger than human players in tactical calculation, but engine output still needs interpretation. Short browser analysis is useful for finding blunders, missed tactics, and candidate moves; deeper or repeated analysis can be helpful in complex positions where the first line may not explain the whole practical lesson.

Is ChessAnalysis Pro really free? What's the catch?

Yes, the chess analysis tool is free to use with no account, trial, subscription, or credit card required. The site may use privacy-respecting analytics and, after AdSense approval, may display advertising to support hosting and maintenance.

Do I need to install software or create an account?

No installation or account required. Chess Analysis runs entirely in your web browser using technology. Simply visit the website from any modern browser (Chrome 87+, Firefox 89+, Safari 15+, Edge 88+) and start analyzing immediately. Works on Windows, macOS, Linux, iOS, and Android. Your analysis starts in under 2 seconds with no downloads, no sign-ups, and no configuration needed.

Is my chess game data private and secure?

Your chess game data is processed locally in your browser by the client-side Stockfish engine. We do not require accounts and do not upload your PGN for engine analysis. The site may still use analytics or advertising cookies for page-level measurement, as described in the Privacy Policy.

What chess formats and platforms are compatible?

Chess Analysis supports standard PGN (Portable Game Notation), the common export format used by major chess platforms and database tools. You can also enter a FEN position for single-position review. If a PGN contains unusual annotations or malformed move text, clean the notation first so the move list can be parsed correctly.

How can I use this tool to improve my chess rating?

Use analysis as a review habit rather than a shortcut. A practical workflow is: (1) Review recent losses to identify patterns; (2) Focus on positions where the evaluation changed sharply; (3) Study the engine's suggested alternatives and explain why they work; (4) Track recurring error types such as tactical misses, time-pressure decisions, weak endgame technique, or poor opening choices.

What analysis depth should I use and how long does it take?

Start with a moderate depth for a fast review, then increase depth on critical positions where the evaluation changes sharply or the suggested line is not obvious. Runtime depends on your device, browser, and position complexity, so mobile devices and older laptops may benefit from lower depth settings.

Can I analyze games on mobile devices?

Yes, fully optimized for mobile. Chess Analysis works on iOS (iPhone/iPad with Safari 15+) and Android (Chrome 87+) with a responsive touch-friendly interface. Mobile analysis runs slightly slower than desktop (typically 30-50% slower due to CPU limitations) but remains highly usable. For best mobile experience: use WiFi for page load, close background apps for maximum performance, and consider depth 12-15 for faster analysis. Full feature parity with desktop version.

Does this work for chess variants like Chess960 or 3-check?

Chess Analysis supports standard chess only (FIDE rules). We use the standard Stockfish build optimized for classical chess. Chess variants such as Chess960/Fischer Random, Three-Check, King of the Hill, and Crazyhouse require specialized rules and engine support, so they are outside the scope of this tool.

Can I share my analyzed games with others?

Yes, use the Share feature to create a link for discussing a game with another player, coach, or study group. Review shared content before sending it, especially if the game is private preparation or from an ongoing event.

Free Online Chess Game Analysis

Stockfish-powered PGN review with local engine analysis and practical training notes

Game Input

Step 1

Choose your game source

Upload PGN File or Paste PGN

Game Board

Step 2

Game Analysis

Step 3

Load a game and click "Analyze" to see move-by-move evaluation

A Practical Chess Review Workflow, Not Just an Engine Score

ChessAnalysis.Pro is designed around post-game study. Stockfish can tell you which move was stronger, but improvement comes from understanding why the position changed. The review flow below helps turn a PGN into reusable chess lessons.

PGN review starts before the engine

A strong review begins by replaying the game and marking the moments where your plan became unclear. The engine score is then used to test those moments, not to replace your own thinking.

Evaluation swings become training notes

When the score changes sharply, compare the best move with the move played and write the chess reason in plain language: king safety, loose pieces, pawn breaks, endgame activity, or a missed forcing move.

Local analysis keeps the workflow focused

The browser runs Stockfish for the game review workflow, so you can paste a PGN, step through positions, and study candidate moves without creating an account or uploading the game for engine processing.

Featured Chess Game Analysis

Three concrete review positions showing how a FEN, an engine score, and a human explanation become a training note.

Queen's Gambit structure

Pin Tactic After 7.e3

FEN before: r1bqk2r/pp2bppp/2n1pn2/3p4/2PP4/2N2N2/PP2PPPP/R1BQKB1R w KQkq - 0 7

+3.5

-2.1

White wants a quiet 7.e3, but the engine review shows that the center is not ready for another slow move. The training note is to check forcing replies before locking in a development plan.

Move reviewed: 7.e3
Theme: slow move before tactics
Training: checks and captures scan

Sicilian Najdorf, move 6

Najdorf Development Order

FEN before: rnbqkb1r/1p2pppp/p2p1n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R w KQkq - 0 6

+0.3

+1.8

The review compares a natural bishop development with the needs of the position: king safety, control of d5, and whether Black can gain time with ...e5 or ...b5.

Move reviewed: 6.Bc4
Theme: d5 control
Training: opening rule, not memorized line

Rook ending, move 45

Rook Activity Before Pawns

FEN before: 8/5pk1/6p1/5r2/8/6PK/5R2/8 w - - 0 45

0.0

+0.9

The engine score changes when the rook becomes passive. The practical lesson is to keep checking distance and avoid defending from a square where the opposing king can improve for free.

Position type: rook ending
Theme: passive defense
Training: active rook placement

How Chess Analysis Works

Three steps for turning a PGN into review notes

Import Your Chess Game

Paste your game in standard PGN notation or load the demo PGN. The analyzer also supports FEN strings for single-position review.

Engine Analyzes Moves

Stockfish evaluates positions in your browser so you can compare the move played with candidate moves at critical moments.

Review Insights & Improve

Navigate move by move, identify evaluation swings, and write a practical note about the tactic, plan, or endgame technique behind the change.

Features of Chess Analysis

Our free chess analyzer combines Stockfish engine technology with a focused review workflow. Analyze games online, study tactical patterns, and turn mistakes into practical training notes.

Stockfish Engine Powered

Use Stockfish engine analysis to review candidate moves, tactical swings, and position evaluations directly in your browser.

Interactive Position Review

Step through positions, compare candidate moves, and inspect how the evaluation changes around the critical moments of a game.

Local PGN Analysis

Your PGN is analyzed locally by the browser engine. The site does not require an account or upload your game for engine processing.

Universal Browser Access

No downloads or installations required. Analyze games from any device with a modern web browser—desktop, tablet, or mobile.

Move-by-Move Breakdown

Navigate through every position in your game with evaluations. Identify turning points, tactical mistakes, and missed opportunities that deserve a training note.

Improvement Insights

Understand evaluation swings and critical moments. Learn from mistakes with alternative move suggestions and strategic explanations.

Practical Study Workflows

Use engine analysis as a structured review process: find the turning point, understand the better move, and turn that lesson into the next training task.

Post-game review

Paste a PGN after a game, scan the evaluation changes, and mark the positions where your plan or calculation went wrong.

Training notes

Turn recurring mistakes into a short study list: missed tactics, poor exchanges, weak king safety, endgame technique, or time-pressure habits.

Coach discussion

Use engine lines as a starting point for explanation, then compare candidate moves and human plans instead of memorizing a single top move.

Private analysis

Run the Stockfish engine in your browser for local analysis of your PGN, useful when you do not want game preparation uploaded for engine processing.

Chess Analysis FAQs

Answers to common questions about using Stockfish engine analysis to review and improve your chess games

Chess Analysis is a free, browser-based chess game analyzer powered by Stockfish. Paste a PGN, choose an analysis depth, and review the engine evaluation, best move suggestions, and marked mistakes move by move. The engine runs locally in your browser, so your PGN does not need to be uploaded for analysis.

Review One Game With a Clear Method

Paste a PGN, review the critical positions, and turn one mistake into a specific training task for your next study session.

No sign-up required
Browser-based PGN review
Practical training notes