TL;DR
Each team gets 2 unsuccessful reviews per innings in Test cricket and ODIs. Successful reviews are not penalised. In T20Is, teams get 1 review per innings. Reviews are retained across innings — they do not reset when the batting changes.
What is DRS?
The Decision Review System gives a team a formal way to challenge an on-field decision and ask the third umpire to examine the available evidence. It appeared in Test cricket in 2008, reached ODIs in 2011 and was extended to T20Is in 2016; it is now part of international cricket's standard decision process.
DRS is not one camera or one test. The review combines ball tracking for LBW calls, Hot Spot and Snickometer evidence for possible edges, plus the relevant replay angles. The third umpire works through that evidence before confirming the original decision or sending a different decision back to the field.
How Many Reviews Per Innings?
| Format | Reviews Per Innings | Reset Between Innings? |
|---|---|---|
| Test Cricket | 2 unsuccessful reviews | No — reviews carry over |
| ODI | 2 unsuccessful reviews | No — reviews carry over |
| T20I | 1 unsuccessful review | No — reviews carry over |
| Domestic / Club | Varies by competition | Varies by competition |
Important: In multi-innings formats (Test and first-class cricket), unused reviews carry over from the first innings to the second innings. If a team has 1 review left at the end of their first innings, they start the second innings with 1 review.
What Can Be Reviewed?
Any of the following on-field decisions can be referred to DRS:
- LBW (Leg Before Wicket): Ball tracking shows whether the ball was going on to hit the stumps
- Catch: Whether the ball was caught cleanly (Hot Spot and Snickometer used)
- Stumping: Whether the batter was out of the crease
- Run Out: Whether the batter was grounded behind the crease
- Bowler's Foot Fault (No Ball): Whether the bowler overstepped
- Batter Hit the Ball Twice: Rare, but can be reviewed
What Cannot Be Reviewed?
- Decision to give out (batter walking): The umpire must have given the decision out
- Dismissals not involving the umpire: e.g., a batter retiring hurt
- The width of a delivery: Wide signals are not reviewable
- Bounces above head height: (though the batter can be out caught off a bouncer)
Ball Tracking — How Does It Work?
Ball tracking is used mainly for LBW reviews. Multiple cameras record the delivery, then software reconstructs the ball's path after the bounce. The projection estimates the continuation of that path and shows whether the ball would have struck the stumps or passed above them.
For an LBW to be given out via DRS, the ball tracking must show:
- The ball pitched in line with the stumps or on the off side
- The ball was going on to hit the stumps (not over or past the stumps)
- The point of impact was in line with the stumps (or outside off stump, if the batter was offering no shot)
Hot Spot
Hot Spot uses infrared cameras to look for the heat created by friction. When the ball meets the bat or pad, that contact can appear as a bright mark, giving the third umpire another way to investigate a possible edge before the ball reaches the keeper or slips.
The clearest results come from firm, direct contact. A faint edge off a boot or pad may leave a weaker signature, so Hot Spot is evidence for the review rather than an automatic answer in every close call.
Snickometer
The Snickometer, commonly called Snicko, listens for the sound produced when the ball brushes the bat. Its microphones create an audio waveform that is matched to the video frame, so a spike at the precise moment of passage can support an edge decision.
Snicko drew major attention during the 2019 Ashes after it helped overturn several not-out calls, including a review involving Steve Smith in the first Test at Edgbaston. Current systems use multiple sensors and are strongest when the sound pattern is read alongside Hot Spot and the replay footage.
ICC 2026 DRS Rules — Key Changes
The ICC Playing Conditions 2026 confirm that each team is permitted two unsuccessful reviews per innings in Test cricket and ODIs, reduced from three reviews per innings that were used in some tournaments between 2019 and 2023. The change was introduced to reduce the number of time-consuming reviews while maintaining the accuracy benefit.
DRS Success Rate — Does It Work?
Studies consistently show DRS overturns approximately 30-40% of reviewed decisions that were initially given out. The system has dramatically reduced the number of "howlers" — obviously incorrect decisions that would have affected match outcomes.
However, ball tracking is not infallible. The "umpire's call" rule — where ball tracking margins within a defined zone are ruled in favour of the on-field decision — remains controversial. Critics argue that "umpire's call" is inconsistent with the spirit of using technology to eliminate error.
Strategic DRS Use — Tips for Teams
- Save reviews for the last 30 overs — LBW and caught-behind decisions in the death overs are most likely to be reviewed by the batting team
- Watch the Snickometer graph — even a small spike can confirm an edge; don't assume silence means clean
- Check Hot Spot before ball tracking — if Hot Spot shows a clear edge, the ball tracking for LBW becomes irrelevant
- Review low-confidence calls — if the bowler and captain look unsure, the on-field call is more likely wrong