Usually, if the ball passes the batsman without being deflected, the wicket-keeper will catch it. This normally prevents the scoring of runs because the batsmen will be unable to complete a run before being stumped or run out by the wicket-keeper. However, if the wicket-keeper fumbles or misses the ball, the batsmen may be able to score runs safely. These runs are scored as byes: they are added to the team's total, but not to the numbers of runs scored by either batsman.
If the wicket-keeper misses the ball and it travels all the way to the boundary, the batting team scores four byes, just as if the batsman had hit the ball to the boundary for four runs. In the virtually impossible case that a bouncer bounces so high that it flies directly over the boundary without touching the ground, only 4 byes are awarded. One cannot score a boundary six in leg byes – or in byes, wides or no balls. A boundary six can only be scored if the ball has made contact with the bat or the hands or gloves holding it.
If the ball was a no ball, any extras scored that would otherwise be byes are instead recorded as no balls, not as byes.
If the ball was a wide, again any extras are scored as wides and not as byes.
Whereas wides and no balls are considered to be the fault of the bowler, and are considered negative statistics in a bowler's record, byes are considered to be the fault of the wicket-keeper, and are considered negatively against the wicket-keeper's record. However, some playing conditions make byes more likely, regardless of a wicket-keeper's ability – wayward fast bowling, or an uneven pitch, or the need for the keeper to stand directly behind the stumps.
Byes are relatively rare in one-day cricket, usually making the smallest component of extras in a score. This is because the batsman is more likely to attempt to hit the ball. They are far more prominent in first-class cricket. For example, in the test series between Australia and England in 2010-11, there were 258 extras in five matches, of which 76 were byes (29.4% of the extras). In the seven one-day and T20 matches that followed between the same sides, there were 262 extras, of which only 10 were byes (3.8% of the extras).
Normally batsmen never attempt to run byes when the wicket-keeper catches the ball. However, in situations at the end of a game when the batting team must score runs quickly in order to have a chance of winning, the batsmen may risk running a bye and hope that the wicket-keeper fumbles the ball or throws it inaccurately when attempting to run a batsman out. The usual result of this is a batsman's being run out, but sometimes the tactic pays off with a few ODI matches having been won on byes.
The test wicket-keeper who has conceded least byes per test (out of all those who have played 10 tests or more) is Denis Lindsay, with 20 byes conceded in the 15 tests in which he kept wicket; most of the best keepers in this regard have averaged around 3 or 4 byes per test. Lindsay conceded no byes at all in his last four tests.
The umpire signals byes by raising his arm into a vertical position, the palm of his hand open to distinguish between the signal for byes and out.
- Law 26 bye and leg bye
- Statistics derived from score sheets in Wisden 2011, pp. 227-46, 862-69.
- S. Rajesh, 'The unsung heroes behind the stumps', http://www.espncricinfo.com/magazine/content/story/220524.html
- Signal for bye