No AI learning tool can do everything, and picking the wrong one wastes more time than picking none. For self-study, what matters is whether you can ask follow-up questions at any time; for exam preparation, whether you can turn your own notes into practice questions and tests; for languages, whether there are real speaking situations and whether the language you want is supported. Decide who you are first, then look at the product.
Four tools: look at each one's weak spot first
- ChatGPT Study Mode: free, included in all personal plans; Go about $8, Plus about $20 and Pro from about $100 a month, all US prices, with the live price on the official website applying. It is a tutoring mode that breaks problems down step by step and gives short quizzes along the way, without handing over the full answer. Not for people who must follow a set textbook strictly or cite sources word for word. One real limitation: it is only a system instruction, not a separately trained model, so performance can be inconsistent, it sometimes still gives the answer directly, and where to find it may vary by version.
- NotebookLM, now Gemini Notebook: free, all you need is a Google account; the free tier is 100 notebooks with up to 50 sources each. Paid upgrades are Plus about $4.99 and Pro about $19.99 a month, all US prices, with the live price on the official website applying. After you upload PDFs, documents, web pages or YouTube videos, it answers from your own material, with clickable citations, and can make summaries and quizzes. Not for people with no material who just want to ask general questions, and not for searching across notebooks. One real limitation: having sources does not mean it never gets things wrong; about 13% of answers still contain hallucinations, so citations need to be checked against the original.
- Khanmigo: the teacher version is free and includes more than 20 lesson-preparation tools; the learner and parent version is about $4 a month or $44 a year, and can only be bought in the United States. Free for teachers does not mean free for students: a student using the tutor at home needs a paid parent subscription or a school contract. Not for families outside China and the United States buying it themselves, and not for people who do not study Khan courses and only want to ask general questions. One real limitation: it is text-only conversation with no voice mode, which makes it unfriendly for younger learners.
- Duolingo Max: about $29.99 a month or $168 a year, all US prices, with the live price in the app applying. Its core is Video Call and Roleplay speaking practice, for English speakers learning Spanish, French, German, Italian, Portuguese, Japanese, Korean or Chinese. Not for people whose language is not on the supported list, and not for people who only want to memorise words, do not want to speak, or want to prepare systematically for a language exam. One real limitation: there has been no official announcement of an end date, so check in the app before buying whether Max is still on sale.
How to choose without getting it wrong
For self-study, use ChatGPT Study Mode; if you want diagrams and video explanations, also look at the free Gemini Guided Learning, but its free model has been downgraded to Flash-Lite and is limited on complex maths. For exam preparation with your own notes, choose NotebookLM. If you study K-12 through the Khan Academy system, a teacher should use Khanmigo for lesson preparation. To practise speaking a language, first check that the language is on the supported list, then consider Duolingo Max; otherwise stick with the free version.
