Clan War Leagues is a season-based league structure for Clan Wars. Once a month, Clans participate in week-long Seasons, during which they fight other Clans of similar skill level each day of the week.
The Clan War Leagues are Bronze, Silver, Gold, Crystal, Master and Champion league.
When a Clan War League Season is about to start, the Sign-Up period begins. Clan Leaders have two days to enter War Leagues matchmaking with at least 15 players selected.
The regular Clan Wars button changes into the Clan War Leagues button when a Clan War Leagues season begins:
By default, all Clan members are in the roster for Clan War Leagues. The roster represents the pool of players who can participate in the Wars of the Season and gain rewards.
Each Season Clans can choose from two war sizes: 15vs15 and 30vs30. In Champion league, only the war size 15vs15 is available.
Clans can decide the war size at the start of each season, and it doesn't affect their league position in any way. If Clans switch between war sizes between seasons, they will continue from the league they reached regardless of which war size they played previously.
If you want to play both a Clan War and Clan War Leagues, you have to join a Clan War in Clan A, and be enrolled to Clan War Leagues in Clan B.
A Clan can only participate in one war type at a time: Clan War Leagues or regular Clan Wars or a Friendly War. If a Clan is participating in Clan War Leagues, they cannot start a Clan War or Friendly war until Clan War Leagues are over.