NACLO

Overview

The North American Computational Linguistics Open (NACLO) is a contest in which students solve puzzles built from language data, using logic and pattern finding. No prior knowledge of linguistics or of other languages is needed. Winners can go on to the International Linguistics Olympiad (IOL), which sends national teams from the US and Canada. Taking part is free for eligible students.

Who can take it

The contest is aimed at high school students, though younger students are welcome. To be eligible, a student must:

• never have been enrolled as a full-time college or university student;

• be under 20 on the first day of the IOL;

• be a citizen of the US or Canada, or be enrolled in a secondary school there.

To be considered for a national IOL team, a student must also meet the IOL's own eligibility rules and can qualify for only one national team in a given year, either the US team or the Canada Anglophone team.

Levels or stages

Open Round

Open to all interested middle and high school students and held at registered sites. In 2026 it ran on 29 January and lasted three hours. Students should expect between 6 and 12 problems, most of them automatically gradable.

Invitational Round

For students who scored highly in the Open Round. The problems are harder. In 2026 it was held on 19 March and lasted four hours. It is also used to pick the national winners who may go to the IOL.

Syllabus

There is no syllabus. Each problem gives all the information needed to solve it. Typical types include translation puzzles, number puzzles and sound-pattern (phonology) puzzles.

Marking and results

Each problem carries a set number of points, with harder problems worth more. The score is the sum across problems. Wrong answers are not penalised, and partial credit can be given for incomplete solutions and good ideas. Calculators, computers, phones and similar devices are not allowed. Results are announced within about five to seven weeks of the contest.

Important dates

• 2026: Open Round on 29 January, Invitational Round on 19 March.

• 2027: Open Round on Thursday 28 January and Invitational Round on Thursday 18 March, per an announcement dated 18 September 2026. Student registration opens on 5 October 2026.

How to apply

Create an account on the NACLO registration system and sign up with a competition site, such as a university or high school site. NACLO does not find a site for you. Students who miss the deadline may register as walk-ins on contest day, but not every site accepts walk-ins. Read the current student handbook before the contest.

Preparation tips

• Work through past NACLO problems and solutions, which are published on the practice page of the site.

• Practise writing down the rule you found as well as the answer, since partial credit is available.