Ranked by frequency × severity × recency over 1277 analysed games (weighted 415.2: 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
76.5 per 100 games (95% CI 42–52 of games)severity 31% win chance per occurrencen = 1006 in 618 games (weighted 317.7)score 605.1trend: not enough data (432 recent / 1 prior)
02Slow eval slides over several quiet moves with no single big error
confirmed
90.1 per 100 games (95% CI 58–67 of games)severity 19% win chance per occurrencen = 1197 in 815 games (weighted 374.1)score 440.0trend: not enough data (520 recent / 3 prior)
12.6 per 100 games (95% CI 4–9 of games)severity 37% win chance per occurrencen = 254 in 117 games (weighted 52.2)score 320.3trend: not enough data (229 recent / 0 prior)
04Reached a clearly winning position (≥ +2) and did not win
confirmed
23.2 per 100 games (95% CI 19–27 of games)severity 50% win chance per occurrencen = 312 in 312 games (weighted 96.2)score 300.6trend: not enough data (142 recent / 0 prior)
05Errors in critical positions after thinking under 5 seconds
confirmed
20.4 per 100 games (95% CI 13–21 of games)severity 20% win chance per occurrencen = 284 in 229 games (weighted 84.9)score 123.9trend: not enough data (142 recent / 0 prior)
06Mistakes and blunders once the game reached an endgame
confirmed
12.7 per 100 games (95% CI 6–12 of games)severity 36% win chance per occurrencen = 167 in 114 games (weighted 52.6)score 110.7trend: not enough data (73 recent / 1 prior)
07Allowed the opponent a fork (blunder-check / prophylaxis)
confirmed
10.3 per 100 games (95% CI 7–12 of games)severity 41% win chance per occurrencen = 129 in 115 games (weighted 42.9)score 84.3trend: not enough data (45 recent / 0 prior)
08Allowed the opponent a royal fork (blunder-check / prophylaxis)
confirmed
5.5 per 100 games (95% CI 3–8 of games)severity 43% win chance per occurrencen = 69 in 65 games (weighted 22.7)score 49.9trend: not enough data (26 recent / 0 prior)
9.0 per 100 games (95% CI 5–11 of games)severity 32% win chance per occurrencen = 109 in 94 games (weighted 37.2)score 44.1trend: not enough data (32 recent / 0 prior)
10Allowed the opponent a mate in n (blunder-check / prophylaxis)
confirmed
2.9 per 100 games (95% CI 2–5 of games)severity 51% win chance per occurrencen = 41 in 40 games (weighted 11.9)score 41.7trend: not enough data (21 recent / 0 prior)
11Missed your own fork (calculation / board vision)
confirmed
4.2 per 100 games (95% CI 2–6 of games)severity 39% win chance per occurrencen = 56 in 51 games (weighted 17.4)score 40.3trend: not enough data (24 recent / 0 prior)
12Missed your own mate in n (calculation / board vision)
confirmed
1.2 per 100 games (95% CI 0–3 of games)severity 55% win chance per occurrencen = 20 in 18 games (weighted 4.8)score 35.9trend: not enough data (16 recent / 0 prior)
13Allowed the opponent a sacrifice (blunder-check / prophylaxis)
confirmed
4.4 per 100 games (95% CI 3–7 of games)severity 37% win chance per occurrencen = 55 in 54 games (weighted 18.4)score 33.4trend: not enough data (18 recent / 1 prior)
14Allowed the opponent a queen fork (blunder-check / prophylaxis)
confirmed
3.1 per 100 games (95% CI 2–5 of games)severity 43% win chance per occurrencen = 41 in 38 games (weighted 13.0)score 32.9trend: not enough data (17 recent / 0 prior)
15Missed your own sacrifice (calculation / board vision)
confirmed
3.5 per 100 games (95% CI 2–6 of games)severity 34% win chance per occurrencen = 48 in 47 games (weighted 14.7)score 32.0trend: not enough data (22 recent / 0 prior)
16Missed your own royal fork (calculation / board vision)
confirmed
1.9 per 100 games (95% CI 1–3 of games)severity 41% win chance per occurrencen = 27 in 23 games (weighted 8.0)score 25.3trend: not enough data (14 recent / 0 prior)
17Allowed the opponent a knight fork (blunder-check / prophylaxis)
confirmed
4.3 per 100 games (95% CI 3–6 of games)severity 41% win chance per occurrencen = 50 in 47 games (weighted 17.7)score 25.1trend: not enough data (13 recent / 0 prior)
18Allowed the opponent a discovered attack (blunder-check / prophylaxis)
confirmed
1.4 per 100 games (95% CI 1–3 of games)severity 35% win chance per occurrencen = 21 in 19 games (weighted 5.8)score 19.2trend: not enough data (13 recent / 0 prior)
19Missed your own knight fork (calculation / board vision)
confirmed
1.7 per 100 games (95% CI 1–3 of games)severity 41% win chance per occurrencen = 22 in 18 games (weighted 7.2)score 13.9trend: not enough data (8 recent / 0 prior)
20Allowed the opponent a promotion (blunder-check / prophylaxis)
confirmed
1.2 per 100 games (95% CI 0–3 of games)severity 54% win chance per occurrencen = 14 in 13 games (weighted 4.9)score 13.5trend: not enough data (5 recent / 0 prior)
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 2026-09-21 07:02 UTC.