Last version of the language tree (August 2018)

A course's skill tree or language tree is the organization of the course's skills into rows representing the order of course progression.


The content of a course varies; some courses may contain more vocabulary skills, more grammar skills, or more skills in general than others. A study published in 2012 found that one would need 34 hours of study in Duolingo to cover the first semester of Spanish in college[1][2].  




Main article: Skill

A skill is an item in the tree that consists of one or more lessons. Skills have a levelling system discussed under Crowns to describe how proficient one is in the skill at any given time. Users must level all the skills on each row of the tree to level 1 before moving to the next row.

Bonus skill slotsEdit

Main article: Bonus skill

Some language trees contain certain slots that can be filled with bonus skills.[3] These can be bought at any time provided that a learner has reached a certain point in the tree. Once the bonus skill has been purchased it remains in the tree permanently.


Main article: Lesson

A lesson in Duolingo consists of many exercises that help teach the core aspects of a skill. The lessons themselves contain various exercises.

Tree progressEdit


A Golden Owl as of August 2014

As a learner advances through the course their crown level goes up and they unlock new skills. Once they have all of the course's skills at level 1 (finished the tree), they will be awarded with a Golden Owl trophy.There are also shortcuts a learner may use to quickly complete the skill tree. These shortcuts include:

  • Placement test - Tests all knowledge of a language tree allowing learners to skip all the skills they already know;
  • Checkpoints - Tests all knowledge of a language tree up to a certain point and once the test is completed it automatically marks all known skills as complete; and
  • Skip level - Tests all knowledge of an individual skill.

Tree updatesEdit

Tree changes

Language course contributors continually tweak and update their skill tree. The appearance of the old tree has been changed previously[4] and new lessons or skills may be added or removed to improve the learning experience.[5][6]