Research into Language Difficulty

CEFR.AI calibrates language difficulty by combining text complexity with task demand.

CEFR.AI triangulation model Equilateral triangle with three evidence anchors: professional materials, CEFR.AI Test scores, and linguistic research. CEFR.AI Calibration Engine Professional Materials CEFR.AI Test Scores Linguistic Research
CEFR.AI Calibration Engine Professional Materials CEFR.AI Test Scores Linguistic Research

How We Calibrate

CEFR.AI Placement Scores

Real learner outcomes from CEFR.AI proprietary assessment.

Take the Test

Linguistic Research

CEFR-aligned evidence on vocabulary, grammar, and skills.

Research Notes
Students reading in a classroom

Tools Powered by CEFR.AI

Official applications built on the CEFR.AI calibration framework.

Analyse

Analyze English texts with CEFR-based scoring for fast, consistent level and difficulty insights.

Level Test

Measure learner proficiency with the CEFR.AI placement test, calibrated on the same research framework.

Coming Soon

An open API and app directory are coming soon so teams can build language products on CEFR.AI scoring.

Frameworks we Trust

CEFR levels from Pre-A1 to C2, including the plus levels of the CEFR Companion Volume.

Latest Research

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2026-03-17

Framework Note

Zone of Proximal Development in Language Learning

The Zone of Proximal Development (ZPD) is one of the most useful ideas in language education, but it is often described too vaguely to guide real decisions. In practical terms, ZPD is the space between what a learner can do independently and what they can do with support. For CEFR.AI,...

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2024-12-26

Research Note

Why Flesch-Kincaid Falls Short for CEFR Classification

Can native-speaker readability metrics really predict CEFR levels? Many online ESL/EFL text analysis tools have defaulted to using the Flesch-Kincaid readability index, simply because no specialized algorithms exist for language learners. Using 59 graded texts, we systematically test whether this widely-adopted solution actually works. While our investigation does reveal a...

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