DRS Explained: How the Decision Review System Works

By the Live Cricket Zone editorial team · Last reviewed 17 September 2026

The Decision Review System lets players challenge an on-field umpire's decision and lets umpires check their own calls with television replays and tracking technology. It was introduced in Tests in 2008 and 2009 and is now used in almost all international cricket and the major franchise leagues. This guide explains who can review what, how many reviews are available and how the technology produces its verdicts.

Player reviews

Either the batter given out or the fielding captain may challenge an umpire's decision on a dismissal by making a T sign with the arms within 15 seconds of the decision. Each side has a fixed number of unsuccessful reviews per innings: three in a Test innings and two in an ODI or T20I innings under current ICC playing conditions (the T20I allowance rose from one to two in 2022). A successful review, one that overturns the decision, does not cost the side anything. Reviews are per innings, so a Test side gets a fresh three when the opposition bats again.

Players may review dismissals only: caught, LBW, bowled, stumped, run out and so on. They cannot review a wide or no-ball call on its own, though in some franchise competitions, including the IPL since 2023, sides may challenge wide and no-ball decisions using the same review allowance.

Umpire reviews

The on-field umpires may refer some decisions to the TV umpire themselves without using a team's reviews: run-outs, stumpings, whether a catch was taken cleanly, whether a ball reached the boundary, and whether a delivery was a no-ball. Since 2020 the TV umpire also checks the front foot on every delivery in international cricket and calls no-balls directly, and since 2023 the on-field umpire's "soft signal" on catches has been abolished, so the TV umpire decides catches on the evidence alone.

The technology

  • Ball-tracking (Hawk-Eye or a similar system) uses multiple high-speed cameras to record the ball's path and projects where it would have gone had it not hit the batter. It is used for LBW.
  • UltraEdge or Snickometer synchronises a stump microphone's audio with slow-motion video. A spike in sound as the ball passes the bat indicates contact; its absence indicates none. It is the main tool for caught-behind and for the "did it hit bat first" question in LBW.
  • Hot Spot, an infrared camera that shows heat from friction where the ball struck, is used in some countries as a second check on edges.
  • Slow-motion and ultra-motion replays cover run-outs, stumpings, catches and boundaries.

How an LBW review is decided

The TV umpire works through the LBW conditions in order. First, was it a legal delivery? Second, did the ball hit the bat before the pad (UltraEdge)? Third, where did it pitch: in line, or outside off, or outside leg stump (outside leg is not out)? Fourth, where did it strike the batter: in line with the stumps, or outside off with a shot offered (not out) or with no shot offered (can be out)? Fifth, ball-tracking: would it have hit the stumps?

Umpire's call

Ball-tracking is precise but not perfect, and the umpire on the field had a real-time view the cameras do not. So for the questions of where the ball pitched, where it struck the batter and whether it would have hit the stumps, the system builds in a margin. If the projection shows less than half the ball within the relevant zone, or the centre of the ball outside a defined area of the stumps, the technology is not considered conclusive and the on-field decision stands, marked as "umpire's call". This means the same ball-tracking picture can be out if the umpire originally gave it out and not out if they did not.

A review that ends in umpire's call is not counted as unsuccessful: since 2017 the reviewing side keeps its review. That change removed the harshest feature of the early system, when a side could lose a review on a decision the technology said was too close to call.

Things to know when watching

  • A batter cannot be given out on review for something that was not appealed for, and a review cannot introduce a new mode of dismissal that the umpire did not consider unless the evidence clearly shows it.
  • If the TV umpire finds a no-ball during a review of a dismissal, the batter is not out and the no-ball is called, regardless of what the review was for.
  • Reviews do not carry over from one innings to the next, and unused reviews are not banked.
  • The final decision is displayed on the big screen as OUT or NOT OUT, and the on-field umpire then signals it.