Half of a CS2 match is decided before anyone loads in. The map veto settles which maps get played, who plays on their best map, and which team starts on the side it prefers. If you watch, bet on or analyze matches, it is the first thing to check.
The Active Duty map pool
Competitive CS2 uses a pool of seven maps called Active Duty. Premier matchmaking and professional events, including the Majors, use the same pool. Valve rotates it from time to time, usually swapping one map out and another in, so the exact list changes over the years. Check the current list in the game or in the event rulebook before you rely on old map stats.
Seven maps is not a random number. It is exactly enough for every standard veto to finish with no maps left over: a best-of-three uses four bans, two picks and a decider, and a best-of-five uses two bans, four picks and a decider.
How a BO3 veto works
The most common order in professional CS2, with Team A being the team that starts:
| Step | Team | Action |
|---|---|---|
| 1 | Team A | Bans a map |
| 2 | Team B | Bans a map |
| 3 | Team A | Picks map 1. Team B chooses the starting side on it. |
| 4 | Team B | Picks map 2. Team A chooses the starting side on it. |
| 5 | Team A | Bans a map |
| 6 | Team B | Bans a map |
| 7 | Left over | The last map is the decider, usually with a knife round for sides. |
Map 1 is Team A's pick and map 2 is Team B's pick, so each team gets to play one map on its own terms. The second round of bans is where strategy shows: teams use it to remove the opponent's strongest remaining map, which decides what the decider will be.
How a BO1 veto works
A best-of-one has no picks in the usual sense. The teams alternate bans until one map is left, and that map is played. With seven maps that means six bans in total. Some events split them unevenly or let the higher seed ban more, so read the rulebook for the exact order.
Because nobody actively chooses the final map, BO1s often land on a map that both teams tolerate rather than one either of them loves. A team with a deep map pool benefits most from this. A team that only has two strong maps can see both banned and end up on its weakest ground, which is one reason BO1s produce more upsets. The BO1 vs BO3 guide puts numbers on that.
How a BO5 veto works
Best-of-five series, usually grand finals, use two bans followed by four picks. Team A bans, Team B bans, then the teams alternate picks for maps 1 to 4, and the last map is the decider. Some events give the team coming from the upper bracket an advantage, such as an extra pick or a one-map head start, so check the format first.
Who chooses the starting side
- On a picked map: the team that did not pick the map chooses whether to start on CT or T. It is the trade-off for letting the opponent choose the map.
- On a decider: usually a knife round, with the winner choosing the side.
- In a BO1: event rules vary. A knife round is common.
Side choice matters because many maps lean toward one side. In CS2's MR12 format each half is only 12 rounds, so a strong first half on the favored side can put a team close to the 13 rounds it needs.
How to read a veto like an analyst
- Know the permabans. Most teams ban the same map in almost every series. Once you know both teams' first bans, the rest of the veto is easy to predict.
- Separate picks from comfort. A team's most-picked map is not always its best map. Check its win rate on that map against similar opponents, not just how often it plays it.
- Watch for map pool changes. When Valve rotates a map in, teams take months to build it up. Results on a new map are noisier than on long-standing ones.
- Roster changes reset the data. Map stats from before a roster change describe a different team. Look at matches since the new lineup only.
- Sample size matters. A 5-1 record on a map is six results, not a pattern. Treat anything under about ten maps with caution.
HLTV shows the veto on every match page and keeps map win rates, pick rates and ban rates for each team. Our roundup of CS2 stats websites covers where else to find this data.
How vetoes affect betting
Match winner odds are set before the veto, so they price in a guess about which maps will be played. Once the veto is public, map winner, handicap and total maps markets reprice. That creates two situations worth knowing:
- Predictable vetoes: if both teams always ban the same maps, the pre-veto price already reflects the likely maps. There is little to gain by waiting.
- Uncertain vetoes: when a team has recently changed its permaban, or a new map entered the pool, the veto carries real information. Waiting for it before betting map markets can be worth more than a slightly better early price.
If you bet maps, convert the odds and compare them with your per-map estimate before placing anything. The odds guide shows how, and our methodology page explains how veto context feeds into the picks we post on today's board.