Ranked by frequency × severity × recency over 6489 analysed games (weighted 1185.2: over-the-board counts fully, blitz a fifth, bullet almost nothing). Confirmed needs 12 or more occurrences; provisional 5 to 11; fewer is a watch. Only confirmed leaks may drive more than a fifth of a week's training. Tactical motifs shown here passed validation against the Lichess puzzle database at 70% precision or better; the rest are tracked but hidden until they do.
01Mistakes and blunders with no tactical shape (judgement, not calculation)
confirmed
86.8 per 100 games (95% CI 49–55 of games)severity 31% win chance per occurrencen = 5876 in 3465 games (weighted 1029.3)score 552.3trend: flat (+6.9% vs previous 60 days, n 837/808)
02Slow eval slides over several quiet moves with no single big error
confirmed
96.7 per 100 games (95% CI 62–67 of games)severity 19% win chance per occurrencen = 6399 in 4251 games (weighted 1145.7)score 370.1trend: flat (+2.1% vs previous 60 days, n 902/866)
41.8 per 100 games (95% CI 15–19 of games)severity 36% win chance per occurrencen = 4551 in 1741 games (weighted 494.9)score 315.4trend: flat (-10.4% vs previous 60 days, n 486/662)
04Reached a clearly winning position (≥ +2) and did not win
confirmed
26.7 per 100 games (95% CI 24–29 of games)severity 50% win chance per occurrencen = 1819 in 1819 games (weighted 316.1)score 270.2trend: flat (-1.6% vs previous 60 days, n 262/271)
05Errors in critical positions after thinking under 5 seconds
confirmed
29.2 per 100 games (95% CI 20–25 of games)severity 20% win chance per occurrencen = 2272 in 1657 games (weighted 346.3)score 116.2trend: flat (-10.2% vs previous 60 days, n 265/319)
06Mistakes and blunders once the game reached an endgame
confirmed
15.3 per 100 games (95% CI 8–11 of games)severity 37% win chance per occurrencen = 1094 in 658 games (weighted 181.7)score 107.2trend: flat (-2.1% vs previous 60 days, n 138/157)
07Allowed the opponent a fork (blunder-check / prophylaxis)
confirmed
9.4 per 100 games (95% CI 7–10 of games)severity 41% win chance per occurrencen = 613 in 556 games (weighted 110.9)score 68.1trend: worse (+39.8% vs previous 60 days, n 87/67)
08Allowed the opponent a mate in n (blunder-check / prophylaxis)
confirmed
3.9 per 100 games (95% CI 3–5 of games)severity 54% win chance per occurrencen = 283 in 264 games (weighted 45.6)score 49.5trend: worse (+36.6% vs previous 60 days, n 55/39)
7.8 per 100 games (95% CI 6–8 of games)severity 33% win chance per occurrencen = 513 in 459 games (weighted 91.9)score 43.3trend: flat (-10.8% vs previous 60 days, n 61/77)
10Allowed the opponent a royal fork (blunder-check / prophylaxis)
confirmed
5.4 per 100 games (95% CI 4–6 of games)severity 43% win chance per occurrencen = 363 in 335 games (weighted 64.0)score 39.7trend: worse (+43.6% vs previous 60 days, n 48/33)
11Missed your own fork (calculation / board vision)
confirmed
5.1 per 100 games (95% CI 4–6 of games)severity 40% win chance per occurrencen = 362 in 331 games (weighted 60.4)score 37.9trend: better (-19.2% vs previous 60 days, n 42/49)
12Allowed the opponent a sacrifice (blunder-check / prophylaxis)
confirmed
4.6 per 100 games (95% CI 3–6 of games)severity 37% win chance per occurrencen = 288 in 269 games (weighted 54.5)score 34.2trend: flat (-5.7% vs previous 60 days, n 38/43)
13Missed your own sacrifice (calculation / board vision)
confirmed
4.4 per 100 games (95% CI 3–5 of games)severity 38% win chance per occurrencen = 295 in 276 games (weighted 51.9)score 33.3trend: better (-27.5% vs previous 60 days, n 36/46)
14Allowed the opponent a knight fork (blunder-check / prophylaxis)
confirmed
4.0 per 100 games (95% CI 3–5 of games)severity 39% win chance per occurrencen = 279 in 258 games (weighted 47.9)score 25.4trend: flat (-1.7% vs previous 60 days, n 30/39)
15Allowed the opponent a queen fork (blunder-check / prophylaxis)
confirmed
2.7 per 100 games (95% CI 2–4 of games)severity 45% win chance per occurrencen = 177 in 169 games (weighted 32.3)score 24.3trend: worse (+103.1% vs previous 60 days, n 30/12)
16Missed your own royal fork (calculation / board vision)
confirmed
2.6 per 100 games (95% CI 2–3 of games)severity 43% win chance per occurrencen = 190 in 178 games (weighted 31.0)score 22.1trend: flat (+3.3% vs previous 60 days, n 23/23)
17Missed your own mate in n (calculation / board vision)
confirmed
1.4 per 100 games (95% CI 1–2 of games)severity 54% win chance per occurrencen = 106 in 100 games (weighted 16.9)score 18.8trend: worse (+43.7% vs previous 60 days, n 19/16)
18Allowed the opponent a discovered attack (blunder-check / prophylaxis)
confirmed
2.1 per 100 games (95% CI 1–3 of games)severity 38% win chance per occurrencen = 144 in 131 games (weighted 24.4)score 17.5trend: worse (+42.1% vs previous 60 days, n 23/17)
19Missed your own queen fork (calculation / board vision)
confirmed
1.7 per 100 games (95% CI 1–3 of games)severity 41% win chance per occurrencen = 123 in 119 games (weighted 20.5)score 15.3trend: better (-20.7% vs previous 60 days, n 17/18)
20Missed your own knight fork (calculation / board vision)
confirmed
2.1 per 100 games (95% CI 1–3 of games)severity 38% win chance per occurrencen = 150 in 134 games (weighted 25.1)score 14.5trend: better (-29.5% vs previous 60 days, n 16/21)
Game data from Chess.com (Published-Data API) and Lichess (open API and CC0 database). Engine analysis by Stockfish. Ratings from FIDE. Board design is our own. Data generated 2026-10-02 20:20 UTC.