Creating Custom Formats

Pokemon Showdown supports custom battle formats through rules and format definitions. You can create formats on your side server or use custom rules in challenges and tournaments.

Format Definition Structure

Formats are defined in config/formats.ts (or config/custom-formats.ts):

export const Formats: FormatList = [
  {
    section: "Custom Formats",
  },
  {
    name: "[Gen 9] Custom Format",
    desc: "Description of your format.",
    mod: 'gen9',
    ruleset: ['Standard', 'Sleep Moves Clause'],
    banlist: ['Uber', 'Arena Trap'],
  },
];

Format Properties

Basic Properties

{
  name: "[Gen 9] My Format",           // Format name (required)
  desc: "Format description",          // Shows in format selector
  mod: 'gen9',                          // Generation mod (gen9, gen8, etc.)
  gameType: 'doubles',                  // 'singles', 'doubles', 'triples', 'freeforall'
  searchShow: false,                    // Hide from search
  challengeShow: false,                 // Hide from challenge window
  tournamentShow: false,                // Hide from tournament creation
  rated: false,                         // Allow rated battles
  team: 'random',                       // Team generation: 'random', 'preset'
}

Rulesets and Banlists

{
  ruleset: [
    'Standard',                         // Standard Smogon ruleset
    'Team Preview',                     // Enable team preview
    'Sleep Moves Clause',               // Prevent multiple sleep moves
    'Species Clause',                   // Limit one per species
  ],
  banlist: [
    'Uber',                             // Ban Uber tier Pokemon
    'AG',                               // Ban Anything Goes Pokemon
    'Baton Pass',                       // Ban specific move
    'Arena Trap',                       // Ban specific ability
    'King\'s Rock',                     // Ban specific item
  ],
  unbanlist: [
    'Blaziken',                         // Unban specific Pokemon
  ],
}

Custom Rules

Bans and Unbans

Pokemon Bans
Move/Item Bans
Group Bans
Complex Bans

- Arceus              # Ban all formes
- Arceus-Flying       # Ban specific forme
- Giratina-Base       # Ban only base forme

- Baton Pass          # Ban a move
- move: Metronome     # Specify it's a move
- Bright Powder       # Ban an item
- item: Metronome     # Specify it's an item

- OU                  # Ban a tier
- Mega                # Ban all Megas
- CAP                 # Ban all Create-A-Pokemon
- Past                # Ban past-gen exclusives
- Mythical            # Ban all Mythicals
- Restricted Legendary # Ban restricted legendaries

- Blaziken + Speed Boost         # Ban combination on one Pokemon
- Drizzle ++ Swift Swim          # Ban combination across team

Value Rules

Rules that accept numeric values:

Max Level = 50                       # Level cap
Min Level = 10                       # Minimum level
Max Team Size = 4                    # Team size before preview
Min Team Size = 4                    # Minimum team size
Picked Team Size = 4                 # Must pick exactly 4 in preview
Max Move Count = 5                   # Allow up to 5 moves
Max Total Level = 200                # Combined level limit
Adjust Level = 50                    # Set all to level 50
Force Monotype = Water               # Require specific type
EV Limits = Atk 0-100 / Def 50-150  # EV range restrictions

Legality Rules

Obtainable                           # Only legal Pokemon/moves/abilities
Obtainable Moves                     # Only learnable moves
Obtainable Abilities                 # Only natural abilities
Obtainable Formes                    # No battle-only formes
Hoenn Pokedex                        # Regional dex restrictions

In-Battle Rules

Team Preview                         # Enable team preview
Blitz                                # 30s preview, 10s per turn
VGC Timer                            # 90s preview, 7min your time, 1min per turn
Sleep Clause Mod                     # Prevent sleep with sleeping allies
Cancel Mod                           # Show cancel button
Inverse Mod                          # Inverse type effectiveness
Dynamax Clause                       # Ban Dynamax

Example Custom Formats

Monotype Format

{
  name: "[Gen 9] Monotype",
  mod: 'gen9',
  ruleset: [
    'Standard',
    'Evasion Abilities Clause',
    'Same Type Clause',              // Force monotype
    'Terastal Clause',
  ],
  banlist: [
    'Annihilape', 'Arceus', 'Baxcalibur',
    'Calyrex-Ice', 'Calyrex-Shadow',
    'Moody', 'Shadow Tag',
    'Baton Pass', 'Last Respects', 'Shed Tail',
  ],
}

Little Cup Format

{
  name: "[Gen 9] LC",
  mod: 'gen9',
  ruleset: [
    'Little Cup',                     // Only unevolved Pokemon
    'Standard',
  ],
  banlist: [
    'Aipom', 'Cutiefly', 'Gastly',
    'Girafarig', 'Scyther', 'Yanma',
    'Moody',
    'Baton Pass', 'Sticky Web',
  ],
}

VGC-Style Format

{
  name: "[Gen 9] VGC 2026",
  mod: 'gen9',
  gameType: 'doubles',
  bestOfDefault: true,
  ruleset: [
    'Flat Rules',
    '!! Adjust Level = 50',
    'Min Source Gen = 9',
    'VGC Timer',
    'Limit Two Restricted',
  ],
  restricted: ['Restricted Legendary'],
}

Custom OM Format

{
  name: "[Gen 9] Almost Any Ability",
  desc: "Pokemon have access to almost any ability.",
  mod: 'gen9',
  ruleset: [
    'Standard OMs',
    '!Obtainable Abilities',         // Remove ability restrictions
    'Ability Clause = 1',            // Limit one of each ability
    'Sleep Moves Clause',
    'Terastal Clause',
  ],
  banlist: [
    'Annihilape', 'Arceus', 'Baxcalibur',
    'Arena Trap', 'Huge Power', 'Moody',
    'Shadow Tag', 'Wonder Guard',
    'Baton Pass', 'Last Respects',
  ],
}

Challenge Format

Use custom rules in challenges with the @@@ syntax:

/challenge username, [Gen 9] OU @@@ -Uber, +Blaziken, Max Level = 50

Tournament Format

Apply rules to tournaments:

/tour rules -Landorus-Therian, -Ogerpon-Wellspring

Creating Custom Format Files

Create custom-formats.ts

Create config/custom-formats.ts in your server directory:

// Note: This is the list of formats
// The rules that formats use are stored in data/rulesets.ts

export const Formats: FormatList = [
  // Your formats here
];

Add Format Sections

Organize formats into sections:

{
  section: "Custom Singles",
},
{
  name: "[Gen 9] Custom Format 1",
  // ...
},
{
  name: "[Gen 9] Custom Format 2",
  // ...
},

Restart Server

Restart your Pokemon Showdown server for changes to take effect:

./pokemon-showdown

Advanced: Format Hooks

Add custom battle logic with format hooks:

{
  name: "[Gen 9] Custom Format",
  mod: 'gen9',
  ruleset: ['Standard'],
  onBegin() {
    this.add('-message', 'Welcome to the custom format!');
  },
  onModifyDamage(damage, source, target, move) {
    // Custom damage calculation
    return this.chainModify(1.5);
  },
  onSwitchIn(pokemon) {
    // Trigger on switch
    this.add('-message', `${pokemon.name} switched in!`);
  },
}

Rule Combinations

Whitelisting

Create an allowed-only list:

- all pokemon, + Charmander, + Squirtle, + Bulbasaur
- all moves, + move: Metronome
- all abilities, + No Ability

Removing Rules

Remove parts of standard rulesets:

! Team Preview                       # Remove team preview
Obtainable, ! Obtainable Moves       # Allow any moves
Flat Rules, !! Picked Team Size = 5  # Override value rule

Testing Your Format

Challenge Format

Test with /challenge command first:

/challenge username, [Gen 9] Custom Format

Create Room

Create a test room to try battles:

/makechatroom [roomname]

Tournament Test

Test tournament integration:

/tour new [Gen 9] Custom Format, elimination

Additional Resources

Custom Rules Reference

Complete custom rules documentation

Rulesets Source

View all available rulesets

Format Examples

Official formats for reference

Mod System

See the Modding guide for custom mechanics

Get Started

Server Hosting

Battle Simulator

Pokedex & Data

Development

Format Definition Structure

Format Properties

Basic Properties

Rulesets and Banlists

Custom Rules

Bans and Unbans

Value Rules

Legality Rules

In-Battle Rules

Example Custom Formats

Monotype Format

Little Cup Format

VGC-Style Format

Custom OM Format

Challenge Format

Tournament Format

Creating Custom Format Files

Advanced: Format Hooks

Rule Combinations

Whitelisting

Removing Rules

Testing Your Format

Additional Resources

Custom Rules Reference

Rulesets Source

Format Examples

Mod System

Build docs developers (and LLMs) love

Get Started

Server Hosting

Battle Simulator

Pokedex & Data

Development

​Format Definition Structure

​Format Properties

​Basic Properties

​Rulesets and Banlists

​Custom Rules

​Bans and Unbans

​Value Rules

​Legality Rules

​In-Battle Rules

​Example Custom Formats

​Monotype Format

​Little Cup Format

​VGC-Style Format

​Custom OM Format

​Challenge Format

​Tournament Format

​Creating Custom Format Files

​Advanced: Format Hooks

​Rule Combinations

​Whitelisting

​Removing Rules

​Testing Your Format

​Additional Resources

Custom Rules Reference

Rulesets Source

Format Examples

Mod System

Build docs developers (and LLMs) love

Format Definition Structure

Format Properties

Basic Properties

Rulesets and Banlists

Custom Rules

Bans and Unbans

Value Rules

Legality Rules

In-Battle Rules

Example Custom Formats

Monotype Format

Little Cup Format

VGC-Style Format

Custom OM Format

Challenge Format

Tournament Format

Creating Custom Format Files

Advanced: Format Hooks

Rule Combinations

Whitelisting

Removing Rules

Testing Your Format

Additional Resources