A mirror match or mirror is a match between two players using roughly the same deck or deck type.
Strategically, mirror matches often present quite a different experience than other matchups, with the player forced to adopt a different approach than usually aimed for. In addition, the precise choice of cards for the deck may vary depending on the predicted percentage of mirror matchups: a deck that is ideally built to face any other class may find itself at a disadvantage when facing a mirror with slightly different tech choices.
Mirror matches between control decks can be extremely drawn-out affairs, with Control Warrior mirror matches especially being some of the longest and slowest in the game. The tendency to focus on reactive gameplay can make these matches extremely passive, while the complex strategies underlying the decks can result in extremely deep decision making. In contrast, mirror matches between aggro decks are generally the quickest in the game, with both decks aiming for victory in the first few rounds, and the decks' reach and lack of defensive cards ensuring neither side lasts too long.
Victory in mirror matches may be decided by several factors, often quite different than those normally focused upon. Aggro decks usually triumph through their reckless and short-lived burst damage, but in a mirror match, victory may be decided by which player is better able to remove the opponent's minions and control the board, exhausting their momentum. Control mirror matches such as Control Warrior may be decided by which deck is able to outlast the other, with play focused on gaining Armor. While such decks usually revolve around drawing cards, in mirror matches these decks may intentionally avoid card draw, and even try to force the opponent to draw cards. Combo decks and control decks revolving around dealing burst damage are usually decided more by who can achieve their win condition first, unless the deck includes a viable means of countering the opponent's coup de grace - in which case play often becomes a waiting game, with each player trying to guess if the other has found their combo yet, and having to choose either to unleash their own finishing move - and risk having it defeated - or lay in wait to ambush the opponent once their patience wears out.
Mirror matches sometimes bring some very specific new factors into play, due to the mutual synergy of the decks. Most commonly, minion type synergies often allow for unexpected plays due to related cards. Perhaps the most dramatic example of this is a Demon Warlock deck featuring , which was once immensely vulnerable to . When Jaraxxus was common in the meta, some Demonlock mirror matches intentionally avoided playing it, even if playing it would apparently spell victory, due to the likelihood of the opponent immediately destroying them. Murloc mirror matches used to be plagued by cross-deck synergy, due to cards like , , , and which used to benefit all Murlocs, regardless of which player they belong to, with only still being able to benefit from the opponent's Murlocs. Similar to the case with Sacrificial Pact, in the right meta may be included in Murloc decks, serving as a kind of self-consuming buff card in most matchups, but also as a very effective counter in mirror matches.