dead man walking
by darkie and tennisace
Updated 12/25/18 by tennisace
What are the tiers?
The main tiers are OU, UU, RU, NU, and PU. The former four stand for Overused, Underused, Rarelyused, and Neverused, respectively. PU does not stand for anything. There are also several banlists, which are UUBL, RUBL, NUBL, and PUBL. UUBL is composed of Pokemon banned in UU, RUBL is composed of Pokemon banned in RU, and so on. The banlists are meant only serve as lists of Pokemon that are too powerful for the given tier.
The Ubers tier is a special case, as it used to be considered as just the banlist for OU. However, it is now officially a tier. The Anything Goes format is a metagame above Ubers, where there are no clauses (except the Endless Battle Clause) and no bans. You can read a more detailed explanation of the philosophy of Ubers and AG here.
What is the purpose of tiers?
Tiers provide a snapshot of what the most important threats in the game are. While any Pokemon can be viable in a higher tier, they show you what Pokemon are most commonly used in the tier that you are looking at. This is extremely helpful when team building to make sure you account for the right threats. There is no use preparing for Musharna when you're playing OU because you will rarely, if ever, see one!
Tiers also serve another important role: it allows for many metagames to take place in order to make all Pokemon viable. For example, Blastoise is almost never seen in OU because it is simply outclassed by too many Pokemon. There is, however, a place where it can excel: NU! Many interesting Pokemon which cannot make it in OU often excel in lower tiers; Pokemon such as Escavalier, Guzzlord, Sylveon, and more all find useful niches there!
Am I forced to use Smogon's tiers?
We only enforce our tiers in our official tournaments, on our ladders, and on Wi-Fi battles that are arranged on Smogon. You may follow whatever tiers you like anywhere else, which includes direct challenges on Pokemon Showdown. In that case, as long as both parties agree, you may use whatever rules you want.
Who uses your tiers?
The primary audience for our tiers and rules are people who play Pokemon competitively and want to play in a 6v6 singles format under rules both players know and understand. They are not intended to replace Nintendo's VGC format nor is the ruleset meant to control how someone chooses to play the game's story. They are simply rules that have evolved over time based in a competitive mindset for competitive players.
How are tiers and banlists determined?
Smogon uses usage as the main metric to determine tiers, which is evident by the full names of the tiers: Overused, Underused, Rarely Used, and Never Used. The banlists, Ubers, UUBL, RUBL, NUBL, and PUBL to balance out the usage-based tiers. Ubers is the banlist for OU, UUBL the banlist for UU, RUBL for RU, NUBL for NU, and PUBL for PU.
Each successive tier is calculated off of the higher tier as follows. Tiers are recalculated every three months using weighted usage statistics. The most recent month is given the highest weight with the two months prior given increasingly lower importance. The aggregate usages of all Pokemon are listed and any Pokemon who fall above the cut-off of 3.406% are counted in that tier. For example, when looking at OU's statistics, everything below the 3.406% cutoff is UU. From UU's, everything below is RU, everything below RU's cutoff is listed as NU, and everything below NU's cutoff is PU.
While that number looks like it was just pulled out of thin air, it is not quite that arbitrary. Any Pokemon whose usage is above the cutoff had more than a 50% chance to be seen at least once in 20 battles on the given ladder. For example, if you play 20 battles on the UU Ladder on a simulator, while it is not guaranteed that you will see every Pokemon that is UU, these are generally the Pokemon that you will be fighting. For this reason, it is helpful to see tiers as sort of threatlists when you're building teams.
Why is usage a good metric for tiering? Why not use something like winrate?
Generally, we assume that most people who play competitive Pokemon play to win, and when people play to win, people generally use what is best. That said, usage is the most objective form of tiering for Pokemon. For example, because Pokemon is not played 1 on 1, winrate is not an accurate measure; while support Pokemon such as Ferrothorn or Blissey might lose to most Pokemon 1 on 1, they are still an important part of a team's structure.
Other objective metrics might include BST or legendary status, both of which are often misleading because a Pokemon is more than just the sum of its stats or an arbritrary recognition as a legendary Pokemon. While some low BST Pokemon like Pelipper or Chansey excel thanks to well-placed stats, good movepool, and useful ability, others with high BST or legendary status, such as Regigigas, Articuno, and Mesprit, fall short because of a bad distribution of stats, poor typing, and/or useless or detrimental ability.
What is the process of banning a Pokemon?
Sometimes when a Pokemon seems too strong for the rest, they are labelled as what we call suspects. Once suspects are named, they can be tested in isolation in what is known as a suspect test. These tests, ranging in time period of 1 week to 1 month, depending on the suspect, allow voters to decide whether or not that Pokemon truly was overcentralizing or not.
People can obtain eligibility to vote by playing in the suspect test and making sure their rating in that test falls above a certain point and that they play in enough games. This is to ensure that voters are informed so they can make an educated vote. Once the test is over, voting takes place in a blind vote, so there is no risk of bandwagoning or one person's opinions shaping another's.
Can Pokemon be unbanned?
Yes, Pokemon bans are not permanent. If there are significant shifts in the metagame, due to new Pokemon being released, new moves for old Pokemon, or new Hidden Abilities becoming available, then banned Pokemon can be re-introduced to the metagame via a second Suspect Test. Unbans occur much in the same way as bans, only the suspect ladder includes an extra Pokemon, the suspect, rather than the normal suspect test, which has all Pokemon except for the suspect.
A prominent example of this is in Generation 5 Neverused, where Jynx was banned early in the metagame, but unbanned after several Pokemon dropped from RU and BW2 changes had taken effect. A similar situation occured in BW when Latios, for the first time, dropped down from Ubers into OU, where it was seen that, without Soul Dew, he was not quite as powerful as people initially expected.
Why did you ban X Pokemon?
More information about past bans can be found on the forums. As a general rule, however, Pokemon are banned when they become too overcentralizing. This is not to say that they don't have counters, but rather, that either everyone runs that Pokemon or everyone runs its counter, which, in the case of some suspects, are often obscure Pokemon which normally would not see the light of day.
For example, in XY, Mega Kangaskhan was considered so powerful that people used obscure, highly specialized counters like Sableye who would otherwise be outclassed and/or more or less useless in a battle.
X Pokemon is strong! Why aren't they OU?
Our tiering is based on aggregate usage over 3 month spans. Every 3 months, our tiers are "refreshed", so to speak, and Pokemon rise and drop based on their usage for the past 3 months. With this in mind, there are many Pokemon that can and do work in tiers higher than the tier they are listed under. The reason it isn't OU, or any other tier for that matter, is simply because it didn't obtain enough usage. It says nothing about the power of the Pokemon in question, but realize that people overall tend to use Pokemon that work and are easy to use. Lower tier Pokemon can perform very well in higher tiers, but often require specialized team support. In those cases, there will be analyses detailing the best strategy to use for the lower tier Pokemon.
Can I use lower tier Pokemon in higher tiers?
As alluded to in the previous answer, yes, of course! You may not use a Pokemon in a tier lower than the one it is officially listed in, but you can certainly use a Pokemon in a tier higher than the one it is listed in. For posterity, the order of tiers from highest to lowest is: Ubers, Overused (OU), Underused (UU), Rarelyused (RU), Neverused (NU), and PU. Smogon Doubles (DOU), Monotype, and Little Cup (LC) are tiered independently of these metagames, and VGC is not tiered at all, but rather uses the current rules for that particular season.
Tiers for LC, Doubles OU, Monotype, etc.?
Tiering for Little Cup, Doubles OU, and Monotype is entirely separate from the main Level 100 Single Battle tiers that includes Ubers, OU, and the lower tiers. Pokemon that are banned in Little Cup, Doubles OU, and Monotype are not automatically banned in standard OU, nor vice versa. The reason for this is simple: the three formats are entirely different play-styles than the normal tiers. Little Cup is played at Level 5, which means stats don't have as much of a range as they would at Level 100. Two Pokemon could have different Base Speed stats but still tie in Little Cup. Doubles OU is, well, 2v2, which means a whole host of other strategies and moves become viable. Monotype is similar to OU, but the ban lists are not the same due to the restraints imposed by the format.
So which tier should I play?
This is the beauty of the tiering system: you can play whichever tier you want to! Whether you enjoy the subtle strategy involved behind battling with NU Pokemon or you enjoy the brutal action of Ubers, there is probably a tier for you! Even if none of the standard tiers gets you your kicks, Smogon also has an Other Metagames forum where people can play with even weirder rulesets, such as STABmons, where Pokemon can use any move they share a type with, or AAA, where Pokemon can use (Almost) Any Ability you want!
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