Ranked by frequency × severity × recency over 6734 analysed games (weighted 1224.3: 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
86.7 per 100 games (95% CI 49–55 of games)severity 31% win chance per occurrencen = 6084 in 3587 games (weighted 1061.7)score 581.1trend: flat (-0.1% vs previous 60 days, n 1016/732)
02Slow eval slides over several quiet moves with no single big error
confirmed
96.9 per 100 games (95% CI 62–67 of games)severity 19% win chance per occurrencen = 6650 in 4417 games (weighted 1186.8)score 397.7trend: flat (+7.3% vs previous 60 days, n 1120/728)
41.8 per 100 games (95% CI 15–19 of games)severity 36% win chance per occurrencen = 4716 in 1793 games (weighted 512.1)score 335.2trend: flat (-13.6% vs previous 60 days, n 644/622)
04Reached a clearly winning position (≥ +2) and did not win
confirmed
26.6 per 100 games (95% CI 24–29 of games)severity 50% win chance per occurrencen = 1879 in 1879 games (weighted 325.7)score 283.2trend: flat (-5.9% vs previous 60 days, n 313/240)
05Errors in critical positions after thinking under 5 seconds
confirmed
29.4 per 100 games (95% CI 20–25 of games)severity 20% win chance per occurrencen = 2358 in 1722 games (weighted 359.4)score 126.3trend: flat (-6.4% vs previous 60 days, n 342/281)
06Mistakes and blunders once the game reached an endgame
confirmed
15.4 per 100 games (95% CI 8–11 of games)severity 37% win chance per occurrencen = 1148 in 691 games (weighted 188.6)score 117.0trend: flat (-1.4% vs previous 60 days, n 190/143)
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 = 636 in 578 games (weighted 114.8)score 74.1trend: worse (+38% vs previous 60 days, n 107/60)
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 = 292 in 273 games (weighted 47.1)score 51.4trend: worse (+18.5% vs previous 60 days, n 62/36)
7.7 per 100 games (95% CI 6–8 of games)severity 33% win chance per occurrencen = 532 in 478 games (weighted 94.5)score 46.1trend: flat (-6.1% vs previous 60 days, n 76/65)
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 = 377 in 348 games (weighted 66.2)score 43.5trend: worse (+85.6% vs previous 60 days, n 62/25)
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 = 374 in 341 games (weighted 62.0)score 39.8trend: better (-15.4% vs previous 60 days, n 53/41)
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 = 298 in 279 games (weighted 56.4)score 36.5trend: flat (-10.7% vs previous 60 days, n 46/39)
13Missed your own sacrifice (calculation / board vision)
confirmed
4.4 per 100 games (95% CI 3–5 of games)severity 39% win chance per occurrencen = 304 in 284 games (weighted 53.5)score 35.4trend: better (-29.5% vs previous 60 days, n 44/41)
14Allowed the opponent a knight fork (blunder-check / prophylaxis)
confirmed
4.1 per 100 games (95% CI 3–5 of games)severity 39% win chance per occurrencen = 292 in 270 games (weighted 50.0)score 29.8trend: flat (+1.5% vs previous 60 days, n 42/37)
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 = 181 in 173 games (weighted 32.9)score 24.4trend: worse (+144.8% vs previous 60 days, n 34/8)
16Missed your own mate in n (calculation / board vision)
confirmed
1.5 per 100 games (95% CI 1–2 of games)severity 54% win chance per occurrencen = 112 in 105 games (weighted 17.9)score 21.8trend: flat (+7.3% vs previous 60 days, n 23/17)
17Missed 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 = 194 in 182 games (weighted 31.4)score 21.2trend: flat (-5.7% vs previous 60 days, n 27/20)
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 = 149 in 136 games (weighted 25.3)score 18.4trend: worse (+81.3% vs previous 60 days, n 27/12)
19Missed your own knight fork (calculation / board vision)
confirmed
2.1 per 100 games (95% CI 1–3 of games)severity 39% win chance per occurrencen = 157 in 140 games (weighted 26.1)score 16.2trend: flat (-10.7% vs previous 60 days, n 22/16)
20Missed 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 = 126 in 122 games (weighted 20.9)score 15.3trend: better (-21.8% vs previous 60 days, n 20/15)
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 2026-10-08 17:53 UTC.