If you work with documents, the three tools you keep hearing about are NotebookLM, ChatGPT, and Sidenote. They overlap just enough to be confusing and differ enough that picking the wrong one for your workflow is genuinely annoying. Since we build one of the three, we'll be explicit about where the other two win, because they do, in specific and predictable places.
The one-line version: NotebookLM is a research workspace you bring sources into, ChatGPT is a general-purpose assistant that can also read files, and Sidenote is a reading layer that answers questions about the document you already have open in your browser, with citations that scroll to the exact sentence.
The three tools, briefly
NotebookLM is Google's source-grounded notebook. You upload or link a set of sources, and it synthesizes across them: answers with inline citations, study guides, and its standout feature, audio overviews that turn your sources into a podcast-style discussion. It expects you to gather material up front; the notebook is the workspace.
ChatGPT is the most capable general assistant of the three. It reasons well, writes well, handles messy multi-step requests, and can read files you upload. Documents are one of many things it does rather than the thing it's built around, and its citation behavior reflects that.
Sidenote is a browser extension (Chrome, Edge and Firefox today, Opera coming soon) plus web app that reads whatever you have open, in place and read-only: PDFs, Confluence, Notion, SharePoint and OneDrive, Google Docs, arXiv papers, any web page. Every answer is grounded in the document's text and carries a scroll-to-source citation; claims that can't be tied to a retrieved passage are dropped before you see them.
The comparison at a glance
| NotebookLM | ChatGPT | Sidenote | |
|---|---|---|---|
| Built for | Multi-source research projects | General-purpose assistance | Reading and questioning docs in your browser |
| Where documents live | Uploaded or linked into a notebook | Uploaded or pasted into the chat | Read in place, where you already are |
| Answer grounding | Grounded in your notebook sources | Blends your file with training knowledge | Grounded in the open document, unsupported claims dropped |
| Citations | Inline, per-source | Inconsistent; varies by mode | Per-claim, click to scroll to the exact sentence |
| Audio overviews | Yes, a standout | No native equivalent | No |
| General reasoning and writing | Limited to your sources | Best of the three | Focused on the document, not open-ended tasks |
| Scanned PDFs | Often import blank without a text layer | Hit and miss | OCR built in (paid feature) |
| Getting started free | Free tier with source limits | Free tier with usage limits | Free plan: cited summaries, explanations, glossaries; chat via 7-day trial or Pro |
Where NotebookLM wins
If your project is "gather twenty sources and work across them for a month", NotebookLM is the right shape. The notebook model rewards curation: synthesis across sources is strong, citations point back into your material, and audio overviews are genuinely good when you want to absorb a corpus while walking the dog. Nothing else here has an equivalent, and we don't pretend Sidenote does.
Its costs are the flip side of the same design: everything must be gathered up front, notebooks have source and size limits, and scanned PDFs without a text layer tend to import blank.
Where ChatGPT wins
For everything around the document, ChatGPT is the best tool on this page. Draft the email the report should become, restructure an argument, write the code the spec describes, reason through an ambiguous question the document only partly answers. Its general capability is the product.
The trade-off is traceability. ChatGPT draws on your file and its training data at the same time, so answers can blend the two without telling you which is which, and asking it to cite sources can produce references that don't hold up. NotebookLM will generally say when something isn't in your sources; ChatGPT tends to fill the gap with its general knowledge, which is exactly what you don't want when the question should be answered from the document alone.
Where Sidenote wins
If the document is already open in your browser, and for most working reading it is, Sidenote removes the step the other two require: getting the document to the tool. There is no upload, no notebook, no silo. You read the Confluence page, the contract PDF, or the paper where it lives, and ask questions in the sidebar.
The second difference is verification depth. A NotebookLM citation points at a source; a Sidenote citation scrolls the live page to the exact sentence and highlights it, and any claim that can't be matched to a retrieved passage is dropped server-side rather than shown with false confidence. When your question is "can I trust this specific number", that's the loop that answers it fastest.
What Sidenote doesn't do: audio overviews, open-ended general reasoning, or month-long corpus projects at NotebookLM's scale (Collections group a focused set of documents, not hundreds).
Privacy and data handling
All three are cloud services, but the data paths differ. NotebookLM processes and stores uploaded sources on Google's infrastructure, and Google states notebook content isn't used to train its general models. ChatGPT may use consumer conversations to improve models unless you opt out, with stronger controls on enterprise tiers, and uploaded files can be retained for the session. Sidenote reads the open document read-only, never trains on your content, and stores document data in a UK region isolated per account. Policies evolve, so check each product's current terms before uploading anything sensitive - is it safe to upload documents to AI? has a checklist that applies to any tool.
So which should you pick?
- Pick NotebookLM for research projects where you'll curate a fixed set of sources and revisit them, or where audio overviews fit how you learn.
- Pick ChatGPT when the document is an input to a broader task: writing, coding, planning, reasoning.
- Pick Sidenote when the job is reading: getting cited, checkable answers from the documents already in your browser, without moving them anywhere. Start at chat with documents or the head-to-head pages for NotebookLM and ChatGPT.
Plenty of people run two of these side by side, and that's a reasonable answer too: ChatGPT for producing, NotebookLM or Sidenote for reading, depending on whether your sources live in a curated corpus or in your open tabs.