YouTube videos, subtitles, books, articles and websites, or any text you paste. You can also ask the agent to write something on any topic.

It analyzes all of your content first: it counts every word and phrase precisely, and how often each one appears. Then it gives you the most frequent ones you don’t know yet. They make up most of the text, so every word you learn makes more of it clear, and you understand it faster.

Any, from your very first words to advanced. A 30-second test sets your level, and every lesson follows it as you grow. Starting from zero? Choose “I'm a complete beginner, skip the test” and get a ready-made path of 31 beginner lessons in order: each one becomes a course in a tap, and the agent keeps its sentences short and explains everything in your language.

Yes, each language has its own page: English, Spanish, Chinese, and Greek. Translations and explanations are available in 45+ languages.

ChatGPT waits for your question and forgets the answer. Subtlex comes to you: it builds each day’s lessons from the words that are due and reminds you to take them. Reviews follow FSRS, a spaced repetition model based on memory research, so each word returns right before you’d forget it. It picks the words worth learning by how common they are and what fits your level, keeps every word you know or learn in your own dictionary, and finds examples of a word across all your courses. This is exact data about you, stored in your account. Neural networks don’t keep data like this. They can only guess it.

Duolingo keeps you busy with points, gems and streaks, and everyone gets the same made-up sentences. Subtlex has no points to chase. Every lesson is made only from your content and your words: the ones you don’t know yet, from the series you watch or the book you read. You read and watch them in context, then listen, speak and write until they stick, so no minute goes to words you’ll never use. And the more content you add and lessons you take, the better the agent knows you and the more precise it gets, from beginner to advanced.

What you spend on AI features. You start with 200,000 free ones, and each action costs what it uses.