An Introduction to Smogon's Tier System

Art by KAIZA.

Smogon's tier system is used to rank Pokémon into several groups based on their perceived power and usage in competitive play. These tiers dictate which Pokémon can be used in the various metagames of competitive play. Each metagame encompasses different Pokémon, and therefore each one is unique in its style of play. The standards set by Smogon's tier system seek to balance competitive battling, ensuring no Pokémon is "too powerful" or overcentralizes the metagame it appears in. This allows players the flexibility to show "flair" in their team design rather than being restricted to using a particular Pokémon to win.

A Pokémon's placement within a tier is by no means set in stone. As people continue to engage in competitive battles, new strategies and movesets arise that may have previously been overlooked. Through increased playtesting, the popularity of some Pokémon may fluctuate. Furthermore, the community may find these Pokémon's strengths and weaknesses to be handled by the metagame differently. Examples of what would prompt a Pokémon's change in tier include the adoption of new competitive movesets or the reduction in use of its counters. With this in mind, the Smogon tier system is reviewed and updated regularly to reflect how specific Pokémon are utilized by our community.

An Overview of the Tiers

Smogon has established six clearly defined tiers. Metagames restricted to a particular tier automatically include Pokémon from lower tiers. In practice, this means that in OU play, Pokémon from the UU, RU, NU, and PU tiers and their respective banlists are also allowed to participate, but Ubers are not.


The Uber tier is based solely on the power of the Pokémon present within it. Pokémon in this tier are considered to be too powerful to participate in the standard metagame. Note that, with the exception of Mega Rayquaza, no Pokémon is banned from competing with those in the Uber tier. The result is a "free-for-all" metagame with no restrictions other than to ensure competitive playability. Those wishing to use Mega Rayquaza can do so in Anything Goes, a philosophically motivated metagame without any bans or clauses to ensure there's always a metagame where a particular Pokémon is usable.

OverUsed (OU)

OU consists of the Pokémon used prevalently by our community. Since these Pokémon are used frequently, they can be assumed to have a strong combination of stats, typing, ability, and movepool, as competitive battlers use them with the intent of winning their battles. All Pokémon present in the OU tier (as well as those present in lower tiers) may participate in what is the standard metagame.

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The Construction of the OU Tier

For RBY, GSC, and ADV, the OU tier is formed based on the experience of our community in regards to which Pokémon are commonly used in Smogon's standard metagame tournaments. In tournaments, people use Pokémon that can compete at the highest level to allow them to win, so naturally they are an excellent means of determining the OU tier.

From DPP and onwards, the current OU tier has been constructed from the league statistics extracted from our battling medium. These statistics provide the number of times each Pokémon was used in the standard metagame league during each month, and those of the three months prior to the OU tier creation are utilized in particular.

The Pokémon usages from Pokémon Showdown!'s main server of the three months prior to the OU update are first extracted. Each Pokémon usage of each month is then divided by the total of the usages during that particular month, so that the probability of that particular Pokémon being used during that month is obtained. Suppose the probability for a particular Pokémon to be used in month m is P_m. These months are ordered in the following manner: if the list is being updated in July, then April, May, and June correspond to months 1, 2, and 3, respectively.

From previous statistics, a small computer program was written to generate an equation that would fit best the predicted probability P with the actual probability for each Pokémon. This equation is the following:

P = (20×P_3 + 3×P_2 + P_1) ÷ 24

The OU tier is comprised of Pokémon whose P value is greater than 3.41%; this number is the usage that Pokémon require in order to be present in at least one out of every 20 Standard metagame teams on average.

UU Banlist (UUBL)

Pokémon in the UUBL tier aren't used enough to be OU but bring imbalance to the UU tier. A UUBL Pokémon isn't necessarily weaker than an OU Pokémon. UUBL Pokémon, however, are used less for reasons such as requiring additional team support or simply being outclassed by another Pokémon in a specific role. It usually takes only one such inadequacy to explain why a given Pokémon is UUBL and not OU.

UnderUsed (UU)

Pokémon in the UU tier are, simply put, underused. That is, when battling in the OU metagame, they will not be seen as much, likely because they are too weak. This weakness is based on a combination of stats, typing, movepool, and ability that restricts effective use of those particular Pokémon in the standard metagame. In UU play, Pokémon above the UU tier are banned, meaning RU, NU, and PU Pokémon are still allowed to participate. The construction of the UU tier from DPP onwards is found from the usage statistics of UU battles and uses the same method as that for the OU tier.

RarelyUsed (RU)

A tier created as of BW, RU is the answer to the sheer number of Pokémon in the 5th generation. RU, essentially, is the UU of UU; that is, it is comprised of Pokémon not commonly used in the UU metagame. At the time, the addition of the RU tier, supplementing UU and NU, made for a situation in which nearly every Pokémon in existence could become a viable addition to teams. Pokémon placed in UU and higher tiers are banned from RU, as well as those explicitly banned in RU due to the imbalance they bring. The RU tier list is built the same way the OU and UU tiers are created. Similarly to in UU, Pokémon that bring imbalance to the RU tier are moved to RUBL, RU Banlist, and are no longer legal in the tier.

NeverUsed (NU)

Pokémon present in the NU tier lack qualities that would allow them to operate effectively, even in the UU (or RU) environment, and are thus not used much even in that metagame. This is generally due to a combination of poor base stats, typing, ability, and movepool. In NU play, only Pokémon in the NU and PU tiers are allowed. The NU tier attempts to place the Pokémon allowed within it on a more equal footing, allowing them to be used without the worry of being overpowered or outclassed by Pokémon in higher tiers. In GSC and RBY, an NU tier does not exist due to a lack of Pokémon to warrant one. Pokémon that are too strong for NU are moved to the NUBL tier and are not legal in NU play.


The most recent addition to the tiers, PU is the NeverUsed of NeverUsed; Pokémon in this tier are not used even in the formerly lowest tier due to poor base stats, typing, or other attributes. The PU tier was added in XY when a dedicated community started playing with the lesser-used Pokémon in NeverUsed and ended up seeing enough activity and contribution levels to warrant officialization, and only Pokémon in the PU tier are legal in PU play. Just like UU, RU, and NU, PU has its own banlist for Pokémon that are overpowered in the tier; such Pokémon are moved to PUBL.