rookbook
How to find every checkmate you missed
Chess.com shows you a missed mate in a game you open, but not how many you've walked past across your whole history, or which ones cost you the game. This guide covers Rookbook's Missed Mates page — what it scans, how it counts, and how to read every column.
What it scans
Rookbook replays each game one move at a time, trying every legal reply before your move to see whether any ends the game on the spot. If one does and you played something else, that's a miss.
The check is exhaustive, not a guess — and it runs on both sides, recording mates your opponents had against you and didn't play.
No Game Review required
Chess.com's Game Review works one game at a time, and only when you ask. A mate in one needs no engine and no review — just the moves every game carries — so the scan covers your entire history, including the hundreds nobody has opened again.
That's the difference between "here's the mate you missed in this game" and "here is every mate you've missed, and which cost you the result". The one exception is accuracy: because Chess.com only publishes accuracy for games that went through review, the Acc and Acc ± columns sit blank for unreviewed rows while everything else fills in.
Mate in one only, on purpose
The scan looks for mate in one and nothing deeper — a floor, not a shortcoming. A mate in one is unarguable: no engine judgement, no "well, it was winning anyway". If you're walking past those, deeper mates aren't the priority yet — and it keeps the full scan fast in your browser.
Try a few
Four real positions from the sample account, in the order the scan found them. In each, a forced mate sat on the board and the player chose otherwise. Click the piece, then the square it moves to.
Start with the plainest. White to play:
Same idea from the other side. Black to play, so the board flips:
This is the pattern worth worrying about: the same mate was available on five consecutive moves — five decisions, each walking past it:
And the one that mattered. Every miss above came in a game that was still won. This one wasn't:
That last position is the whole argument for the page. Three of these four misses cost a move or two; the fourth threw away a won game. No amount of staring at the raw miss count tells you which was which — that's what the …and not won figure and the Cost column are for.
One oversight, not three
Most naive counters get this wrong. A mate that sits on the board for three of your moves while you play something else isn't three missed mates. It's one mate you didn't see and walked past three times.
Rookbook collapses a run like that into a single miss and records the move count in the Chances column, so a row showing 3× is a worse story than three separate rows would be.
The same rule applies to opponents' misses, so "They missed" counts oversights, not positions. Counting per position inflates both numbers — most in the games where the pattern is most obvious.
The summary strip
Across the top sit the totals for whatever games your filters include:
- Mates found — forced mates you spotted and played, including ones taken a move or two late.
- Mates missed — distinct oversights, using the collapsing rule above.
- Moves walked past — total moves played while a mate sat on the board. A big gap versus Mates missed means you walk past the same mate repeatedly rather than miss it once.
- Conversion — how often you took the mate when it was there.
- Games affected, and …and not won — the second stings: games where you missed a mate and still didn't win.
- They missed, and …and you won — mates opponents had against you, and how many you won. Completed swindles.
- Leaked 3+ after — misses after which you lost three or more points of material by the end.
Reading a row
The columns that carry the most information:
- Move — where it happened, as a fraction.
10/12means the mate first appeared on move 10 of a 12-move game. - Chances — how many of your moves that same mate stayed available for.
- Mate available and You played — the move that ended it, and the one you chose.
- Cost — Stockfish's verdict on the position immediately after the move you played. A big plus means the miss was harmless and you were still crushing; near zero or negative means that move threw the win away.
- Think — seconds spent on the move you missed. Under three seconds means you never looked.
- Clock — time remaining when the mate first appeared. The same miss with eight minutes on the clock versus twenty seconds are different mistakes: one is blindness, the other a scramble.
- Mat then, Mat end, Swing — your material edge when mate was available, at the end, and the change between.
Think and Clock are the diagnostic pair. A long think on a comfortable clock means you looked and didn't see it — a pattern-recognition gap. Two seconds with thirty on the clock isn't about pattern recognition at all.
5× chances, 1.2 seconds on the move played instead — the same mate stood there for five moves, never looked at.Why Cost fills in gradually
Everything except Cost is instant — finding mate in one needs no engine. Cost does: a short Stockfish search per miss to see whether that move mattered.
So it fills in gradually while the page is open, pausing when you navigate away and resuming next visit. Results are cached, each position evaluated once, and the column stays blank rather than guess if the engine's unavailable.
What to actually do with it
Three passes, in this order:
- Sort by Cost and look at the misses near zero — the ones that changed a result rather than delayed one.
- Scan the Think column for anything under three seconds. That's not a chess problem but an attention one — the cheapest thing on this page to fix.
- Look at Chances above 1×. A mate you walked past three times is a pattern your eye doesn't register — usually a back-rank or smothered shape. Two or three in a row show you which.
Star anything worth returning to; the ★ filter chip shows only starred games.
The caveats, plainly
Mate in one only, so a missed mate in three won't appear. Games need move data, which almost all Chess.com games have. And having a mate available means you were already winning, so most misses cost moves, not the game — the summary's "and not won" figure is the honest measure of the damage, not the raw miss count.
Free, no account, and your games never leave your browser.
Find your missed mates on rookbook.net →Common questions
How do I find checkmates I missed? Rookbook replays every game in your history and tests each of your turns for an available mate in one, then lists the position, the move you played instead, and what it cost.
Does it find longer mates? No — mate in one only. It's a deliberate floor: those are unambiguous, need no engine to confirm, and if you're missing them, deeper mates aren't the priority.
Why is the Cost column slow? It runs a short engine search per miss, only while the page is open, and caches the result. Leave the page open after a big import and it fills in.