A league (more precisely called weekly leaderboard or simply Leaderboards) is an XP competition initially available for Android and iOS users. In May 2019, Leaderboards were added for desktop users.
The contest of Leaderboards runs as follows:
One league consists of one of the 10 possible gem ranks, ranked from lowest to highest: Bronze, Silver, Gold, Sapphire, Ruby, Emerald, Amethyst, Pearl, Obsidian and Diamond.
Each user is assigned to a league that consists of 50 random participants of a common rank who earned their first XP of the week at a similar time.
Any valid method of XP-earning (except for the placement test) counts toward the overall amount of XP earned for the ongoing competition.
By the end of all competitions, those who keep their ranks within the promotion zone are promoted one rank higher. Initially, participants must reach the top 10 for promotion for most ranks. Currently it is as follows:
Bronze: Top 20
Silver: Top 15
Gold: Top 10
Sapphire: Top 10
Ruby: Top 10
Emerald: Top 10
Amethyst: Top 10
Pearl: Top 10
Obsidian: Top 10
Diamond: No further advancement
In addition, players who earn either 1st, 2nd or 3rd position in their groups will also earn lingots, denoted in the league area by a gold, silver, or bronze chest by their name, by an amount which increases as they progress through the leagues, as shown in the following table. iOS gems may be awarded in place of lingots, at a rate of 100 gems per 5 lingots elsewhere.
Players who are below 45th position will be demoted one rank lower. In the Bronze competition, there is no demotion as there is no lower rank.
Otherwise, players will remain in the same rank.
In order to participate in a league competition:
At least 10 lessons must already be completed (in any number of trees) prior to the new competition. Any test or story that gives 1 XP or more counts as one lesson.
When the competition refreshes, the new time limit is shown below the set of rank badges.
A sleeping Duo appears along with a message when a lesson is not completed.
As of July 2019, for certain users, for each competition, each group of common league ranks is given a group goal to work together in reaching certain group ratings (rankings) of XP.
When two or more participants accumulate the same amount of XP in the same competition, their rankings are ordered by completion time from earliest to latest.
There are three concepts that can be called league or leaderboard.
The official name of the contest is Leaderboards (or simply leagues)
Each of the updated ranks in which the game is divided is called a league.
Each group of 50 people who compete together is called a league or a leaderboard.
Some users report earning additional lingots on the Android version of the app, with some reporting earning 15 lingots for getting 3rd place in a league and others reporting receiving 30 lingots instead of 20 for getting first place.
Many bots have been spotted on these leaderboards so be wary and report any suspicious behavior to the Duolingo Team.