You've got a pharmacology lecture, three readings and a tutorial sheet. You open ChatGPT, paste in the slides, and ask what a beta blocker does. It gives you a lovely answer that mentions two drugs your lecturer never covered. You open NotebookLM, upload the same files, and ask the same question. It gives you a plainer answer with little citation numbers pointing at slide 14.
That difference is most of the decision. Use NotebookLM when the job is understanding your own course material, because it answers from your sources and shows you where. Use ChatGPT when you need something your material doesn't have: a different explanation, a worked example, help planning your week, or practice that goes beyond the slides. Neither one, on its own, is a study system that gets you to exam day remembering things. I'll get to that.
I build The Study Mill, so I'm biased. I use both of these tools myself and I'll try to be straight about where each is better.
What NotebookLM is best at
NotebookLM is Google's "talk to your documents" tool. You create a notebook for a unit, add your lecture PDFs, slides, readings or links, and everything it says is drawn from those sources, with citations you can click to check.
That grounding is the reason to use it. For a law student working through a reading pack, or a nursing student with a dense A&P chapter, it means the answer matches what your course actually taught, in the words your lecturer used. When it doesn't know, it's more likely to say the sources don't cover it than to invent something.
It has grown well beyond chat. At the time of writing the free plan includes Audio Overviews (two AI hosts discussing your sources), mind maps, study guides, and flashcards and quizzes made from your notebook. Third-party guides put the free limits at around 50 sources per notebook, which is plenty for a semester of one unit. Google says these limits change, so check its help pages.
Where it's weaker: it's only as good as what you put in. If your lecturer's slides are bullet points with no explanation, NotebookLM can only rearrange those bullet points. And it won't go and find a clearer analogy from outside your sources, because staying inside them is the whole design.
What ChatGPT is best at
ChatGPT knows a huge amount about almost everything, and it's very good at explaining the same idea five different ways until one lands. If you're stuck on why the Frank-Starling mechanism matters, or what "ratio decidendi" really means in practice, a conversation with ChatGPT will often get you there faster than rereading your slides.
It also has a Study mode (under "Study and learn" in the tools menu), which pushes it to ask you questions and guide you step by step instead of handing over the answer. It's available on the free plan, with tighter message limits than the paid plans. ChatGPT Plus costs around US$20 a month at the time of writing.
Where it's weaker: it doesn't stick to your course unless you make it, and even then it drifts. Ask about drug classes and you'll get the textbook version, which may not match how your unit grouped them or which ones your exam will test. It can also be wrong with total confidence on specifics like doses, case names and dates. And unless you set up a Project, every chat starts from a blank box. Prompts that make ChatGPT more useful for study.
Side by side
| NotebookLM | ChatGPT | |
|---|---|---|
| Answers from your uploads | Yes, with citations | If you paste them in, and it drifts |
| Explains beyond your material | No, by design | Yes, very well |
| Risk of confident mistakes | Lower | Higher on specifics |
| Quizzes and flashcards | Yes, from your notebook | Yes, if you ask (Study mode helps) |
| Audio | Audio Overviews you listen to | Voice chat |
| Remembers your course between sessions | Yes, per notebook | Only inside a Project |
| Tracks what you keep getting wrong | No | No |
| Free plan | Generous | Usable, with message limits |
Which one for which job
"I don't understand this week's lecture." Start in NotebookLM so you're working from what was actually taught. If its explanation is still too close to the slides to help, take the specific concept to ChatGPT and ask for an analogy.
"I need to check what my lecturer said about X." NotebookLM, every time. The citations let you jump straight to the slide.
"I need a worked example or a practice problem the slides don't have." ChatGPT. Statistics, drug calculations and accounting are where this matters most. Check the working, because it does make arithmetic slips.
"I want to hear my readings while I walk." NotebookLM's Audio Overview is a good first pass on something intimidating.
"Plan my revision around my shifts." ChatGPT. It has no reason to be inside your sources for this.
"Quiz me." Both can now. NotebookLM's quizzes stay closer to your material. ChatGPT's Study mode is better at back-and-forth, like asking you to explain your answer. One warning for either: AI-written multiple choice has tells, like the right answer being the longest option. What we found when we checked ours.
Where both fall short
Neither tool remembers what you got wrong. You can answer ten questions on Tuesday, miss three, and nothing will bring those three back on Friday when you're most likely to have forgotten them. That spacing is one of the most reliable findings in learning research, and it's the part students skip when every session starts fresh.
There's also the comfort problem. Chatting with your material feels productive. A clear answer you followed easily feels like knowledge. But recognising an explanation is a different skill from producing the answer on a blank exam page, and only the second one gets marked. Why rereading feels better than it works.
This is the gap The Study Mill is built for. You upload each week's slides, PDFs, notes or lecture recordings, and it turns them into short lessons, flashcards, and a quiz where you write answers in your own words and they get marked. A daily review brings back the questions you missed. There's a tutor for "explain that differently", and Walk & Learn teaches the week as audio, then asks you questions you answer out loud. Everything stays grounded in what you uploaded, like NotebookLM, but the point is to test you rather than answer you. It's free for 2 classes; Pro is A$7.99 a month and adds unlimited classes, exam mode and cram sheets, with 50% off for students with a .edu or .edu.au email.
To be fair to both: if all you need is to understand a stack of readings, NotebookLM is excellent and free, and nothing I build beats it at that. If you need a patient explainer for anything at all, ChatGPT is hard to match.
A setup that works
- One NotebookLM notebook per unit for understanding and checking what was taught.
- ChatGPT on the side for the concepts that still won't click, and for planning.
- Something that tests you on a schedule, so what you understood this week is still there in exam week.
You don't need all three on day one. If you're only going to try one change, try being quizzed on last week's lecture before you read anything new.
Try it on one lecture
Take one lecture you've already chatted about in NotebookLM or ChatGPT and upload it to The Study Mill. In about a minute you'll have a quiz from it. See how much of what felt familiar you can actually answer.
This is general study advice. Other apps' prices and features are as published in October 2026 and change often. Check their own pricing pages.