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 (DRS) is a technology-assisted process that allows on-field umpires to refer decisions to the third umpire. Introduced in Test cricket in 2008 and extended to ODIs in 2011 and T20Is in 2016, DRS has become standard across all international cricket.
The system combines multiple technologies to assist umpire decision-making: ball tracking (for LBW), Hot Spot (for edges), Snickometer (for edges), and real-time camera angles. The third umpire can check all available evidence before confirming or overturning the on-field call.
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 (used primarily for LBW decisions) uses multiple camera angles and computer algorithms to calculate the trajectory of the ball after it pitches. The system extrapolates where the ball would have travelled — whether it would have gone on to hit the stumps, or whether it would have passed over the top.
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 detect heat friction — when the ball contacts bat or pad, the contact point shows up as a bright heat signature. This is particularly useful for edge detection: if the Hot Spot shows friction between ball and bat, the ball grazed the edge before going to the keeper or slips.
Hot Spot is most reliable when the ball makes clean, firm contact. Edges that go off the boot or pad produce fainter signatures and can be harder to adjudicate conclusively.
Snickometer
The Snickometer (Snicko) uses highly sensitive audio microphones to detect the sound of ball hitting bat. A spike in the audio waveform at the point of contact, synchronised with the video footage, confirms whether the ball kissed the edge.
The Snickometer became famous in the 2019 Ashes when it overturned multiple on-field not-out decisions — most notably against Steve Smith in the first Test at Edgbaston. Modern Snicko uses multiple sensors and is considered highly reliable when combined with Hot Spot.
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