DRS in Cricket Explained: How the Decision Review System Works, and What the Scorer Tracks

Most explanations of DRS stop in the same place: ball-tracking, Hawk-Eye, maybe a paragraph on UltraEdge. That covers the technology, but it skips the part that actually matters to anyone keeping score rather than just watching the review graphic — how many reviews each side has left, what happens to that count depending on how the review comes back, and exactly what changes in the book once the third umpire’s decision is confirmed.

This guide covers the full system: what DRS actually checks for each type of dismissal, how many reviews each format allows, the 15-second signal that starts the clock, what “umpire’s call” really means, and — the part a generic explainer never gets into — what a scorer has to track the moment someone makes the T-sign.

What DRS Actually Is

The Decision Review System is not one piece of technology — it is a protocol for combining several of them with a human decision-maker, the third umpire, who has access to all of it and the on-field umpires don’t:

• Ball-tracking (Hawk-Eye): multiple cameras triangulate the ball’s flight to project where it would have gone had it not been intercepted — used almost entirely for LBW reviews.
• UltraEdge / Real Time Snickometer: a stump microphone feeds an audio waveform synced to the video, so a spike in sound at the moment the ball passes the bat shows an edge too fine to see or hear live.
• Ball-tracking replay and freeze-frame: for run-outs, stumpings and close catches, no projection is needed — just a high-speed camera angle and a freeze-frame at the decisive instant.
• The third umpire: reviews the relevant technology for that specific dismissal type and communicates a decision back to the on-field umpire, who then signals it.

For the LBW-specific mechanics — the pitching, impact and wicket zones ball-tracking has to clear in sequence — see our full LBW rule guide, which covers that in depth. This guide focuses on the system as a whole, across every dismissal type DRS touches.

How Many Reviews Each Team Gets, by Format

Per ICC’s own Playing Conditions appendices for each format. Only a review categorised “unsuccessful” — the on-field decision stands unchanged — counts against this total.

The category is what matters, not just the outcome. A review is successful if the original decision is reversed, and it does not cost the team anything. A review that comes back umpire’s call also does not cost the team anything, because the technology is confirming the on-field call was within its own margin of doubt rather than proving it right or wrong outright. Only a review where the technology clearly backs the original decision — the one that actually loses — is “unsuccessful” and burns one of the team’s allowance. This is why a team can review three or four close shouts across an innings in a format with only one unsuccessful review allowed, as long as enough of them come back umpire’s call or successful.

Calling for a Review: The 15-Second Signal

A review has to be requested inside 15 seconds of the ball becoming dead — the clock most broadcasts show counting down on screen. Only two people can actually call it:

• The batter given out can call for their own review, signalling with a “T” shape made with both forearms above the head.
• The fielding captain can call for a review of a not-out decision — an appeal that was turned down.

Teammates can and constantly do advise — the non-striker walking across to talk it over, a wicketkeeper convinced there was an edge — but the final call belongs to the batter under threat or the fielding captain alone. If the 15 seconds run out before the signal is given, the on-field decision is final and no review is possible, however strongly the players felt about it after the fact.

What Happens for Each Type of Review

The technology consulted depends entirely on what is actually being disputed:

• LBW: ball-tracking checks pitching, impact and wicket zones in sequence — covered in full in our LBW rule guide. This is the only review type where “umpire’s call” applies to a projected trajectory rather than a directly observed instant.
• Caught behind or bat-pad: UltraEdge/Real Time Snickometer audio is checked against the video frame-by-frame for a spike as the ball passes the bat, alongside slow-motion replay for any visible deviation off the bat.
• Run-out or stumping: high-speed replay and a freeze-frame at the moment the bails are dislodged against the moment the bat or a body part grounds behind the crease. There is no tracking margin here — it is a direct visual read, so there is no “umpire’s call” category for a run-out review the way there is for LBW.
• Boundary catches: replay checks whether the fielder’s boot, hand or the ball itself touched or crossed the boundary line during the catching action — a rule that changed for 2026, covered in our guide to the 2026 ICC playing conditions.

Umpire’s Call, in Plain Language

“Umpire’s call” trips people up because it sounds like a non-answer, but the logic is simple: every tracking system has a margin of error, and when the tracked position of the ball falls inside that margin rather than clearly inside or outside the target zone, the system cannot honestly say the original call was wrong. Rather than force a coin-flip overturn, DRS defers to whatever the on-field umpire originally decided. That is why two LBW shouts that look identical on the replay graphic can have opposite outcomes — one was given out and stayed out on umpire’s call, the other was given not out and stayed not out on umpire’s call. The system confirmed both original calls were within its margin of confidence; it did not decide either one was correct in some absolute sense.

The concept extends beyond LBW wherever a projection or a fine margin is involved. During IPL 2026, a widely reported Gujarat Titans–Mumbai Indians match saw a waist-height no-ball review for Tilak Varma come back umpire’s call after the tracked height sat right on the calibrated no-ball threshold — neither clearly above nor clearly below it, so the on-field call stood. It is a useful, current illustration of the same underlying idea: umpire’s call is the system being honest about its own precision, not the technology failing.

What the Scorer Has to Track During a Review

This is the part no generic DRS explainer covers, and it matters as soon as any level of your competition uses even an informal review process:

• Reviews remaining, per team, per innings — not per match. Reset the count to full at the start of each new innings regardless of how many either side used, or had left over, in the innings before.
• Only “unsuccessful” reviews decrement the count. A successful review or an umpire’s-call result leaves the team’s remaining total untouched — track the category of the outcome, not just whether the review happened.
• Don’t finalise the ball until the review resolves. Treat the on-field signal as provisional the moment the T-sign goes up — runs, the wicket, and any extra on that delivery should only be locked into the book once the third umpire’s decision comes back, since a reversal can change the dismissal type, the bowler-fielder credit, or whether the ball produced an extra at all.
• A reversed no-ball call changes the next delivery. If a review overturns an on-field “no-ball” to a legal delivery (or the reverse), it can retroactively affect whether the following ball is a free hit — worth double-checking rather than assuming the free-hit status from the original on-field call.
• Notation stays the same either way. Once a review is resolved, the dismissal is recorded exactly as it would have been if given correctly first time — there is no special notation for “given out, review overturned to not out” beyond simply recording the batter as not out and the delivery as it actually played out.

Does Club Cricket Have DRS?

No. Ball-tracking, UltraEdge and a third umpire watching multiple camera feeds require broadcast infrastructure that only exists at international and major franchise-league level. Law 36 and the rest of the Laws of Cricket apply identically at every level of the game — a club, school or local league umpire is making the same calls DRS checks, in real time, with the naked eye and no replay to fall back on. That is exactly why understanding the underlying Law (rather than just “what the technology showed”) is worth more to a club player or scorer than knowing how Hawk-Eye works.

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Frequently Asked Questions

How many DRS reviews does each team get?

One unsuccessful review per innings in ODIs and T20Is, two unsuccessful reviews per innings in Test cricket. A review that overturns the on-field decision is “successful” and does not count against that total, and neither does a review that comes back “umpire’s call” — only a review that is fully upheld against the team that called it burns one of their reviews.

What is “umpire’s call” in DRS?

It means the ball-tracking or replay evidence overlapped the required zone by less than the margin the technology needs to be confident, so the on-field umpire’s original decision stands rather than being overturned. It is not a weaker version of “out” or “not out” — it means the review system is deferring to the human decision because its own tracking margin is wider than the gap being argued over.

How does a player actually call for a review?

The batter being given out, or the fielding captain, makes a “T” shape with both forearms above their head within 15 seconds of the ball becoming dead. Any other player can advise their captain to review, but only the batter under threat or the fielding captain can make the call — a bowler or a wicketkeeper cannot signal for review on their own initiative.

Does DRS apply in club or school cricket?

No. Ball-tracking, UltraEdge and the third umpire only operate at international and major franchise-league level, where the broadcast infrastructure exists to support them. Law 36 and the rest of the Laws of Cricket are identical at every level — a club umpire is making the same calls with the naked eye and no review available.

What technology does DRS use for a caught-behind review versus a run-out review?

A caught-behind or bat-pad review checks Ultra-Motion replay alongside UltraEdge (or Real Time Snickometer) — an audio spike synced to the ball passing the bat to detect a fine edge the naked eye missed. A run-out or stumping review uses high-speed replay and a freeze-frame at the moment the bails come off, with no tracking margin involved — it is a binary, visually confirmed call rather than a projected one.

Do unused reviews carry over to the next innings?

No. The review count resets at the start of every innings, regardless of how many a team had left over from the previous one. A team that used zero reviews defending 350 in the first innings still starts its own innings with a full allocation.