Omphalis is a reading app for dense sources you come back to: PDFs, papers, articles and long talks. Omphalis is for recurring work with dense sources that matter. You finish reading them, mark confusing or important passages, keep notes attached to the source, and come back later. Omphalis is not a knowledge base and not a summarizer.
The short answer
If you want a NotebookLM alternative for reading a PDF with notes beside the text, try Omphalis.
In Omphalis, a highlight stays on the passage in the source, with your note beside it. Opening it takes you back to that passage with the text around it still in view.
A PDF in Omphalis opens as a cleaned reading page. You highlight it, write notes and open explanations beside a hard passage. PDFs are read on paid plans from $9 a month. 30-day trial, no card required. Includes 200 voice minutes, 200 PDF pages and 15 assistant answers a day.
You can ask Omphalis about the source you have open. Each answer cites the passages it used.
Keep NotebookLM if you want study guides, mind maps or Audio Overviews made from a set of sources.
NotebookLM and Omphalis both let you ask questions about sources and follow citations back to them. NotebookLM is good at answering across a notebook of sources, and at turning them into study guides, briefings, mind maps and Audio Overviews. If that is the whole job, stay. If you still haven't finished the 60-page PDF, a study guide won't do it for you. Omphalis is for that part.
Try Omphalis when you need to stay with one hard source. You read a cleaned page, open an explanation beside the passage that stopped you, mark it, write a note next to it, and listen to the piece itself read aloud.
30-day trial, no card required. Includes 200 voice minutes, 200 PDF pages and 15 assistant answers a day. After that, Free stays free. See plan allowances.
Disclosure: this comparison is written by Omphalis about its own product, so it is not a neutral review. We are not paid by NotebookLM or by anyone else to be compared favourably, this page carries no affiliate links, and every claim about NotebookLM is checked against their own public documentation. Read the full disclosures, and tell us if something here has gone out of date.
Upload a PDF, paper, or transcript into a notebook, then ask across the set and turn it into study guides or briefings. Good when the job is questions across the notebook or Audio Overviews. Less suited to staying inside one dense passage until you get it.
In Omphalis, the PDF opens as a cleaned reading page with its sections alongside. Find your place, open an explanation beside a hard passage, highlight it and write a note next to it. Ask about the source while it stays in view. Each answer cites the passages it used.
Study a set of sources at once
In NotebookLM
Studying a whole source set at once is where NotebookLM (Gemini Notebook) is strongest: questions across the notebook with citations, study guides, briefings, mind maps, and Audio Overviews that discuss the material.
Omphalis keeps related sources in a notebook when a project you keep coming back to needs them together. Your notes stay attached to each source. You still read each piece. Omphalis doesn't build study packs.
Listen without leaving the piece
In NotebookLM
Audio Overviews turn your sources into a spoken discussion or a short brief, in Deep Dive, Brief, Critique or Debate formats.
Omphalis reads the actual source text aloud in a natural voice. The page stays open, so you can mark a passage and come back to it.
A notebook in Omphalis
NotebookLM gives you study material across a source set. This Omphalis notebook keeps two related sources and a note together for one project. It's most useful once you've read the pieces themselves.
Finding our first users brings two Paul Graham essays and a note together. The answer shown cites the startup ideas essay.
Compare the task you came to do
NotebookLM and Omphalis by task
Task
NotebookLM
Omphalis
Questions
Chat across the sources in a notebook, with inline citations.
Omphalis answers questions about the source you have open, typed or out loud in the web app, and cites the passages it used.
Reading
Upload PDFs, websites, YouTube videos, audio files, Docs or Slides into a notebook.
Omphalis opens each source as a cleaned reading page with sections. A PDF is read on paid plans, or within the trial’s 200 PDF pages.
Notes
Write your own notes or save chat responses as notes. Selected notes can also be used as sources for questions and study material.
In Omphalis, your highlight and note stay on the passage. Opening a mark takes you back to it in context.
Listening
Audio Overviews: a spoken discussion or short brief about your sources.
Omphalis reads the source aloud in a natural voice while the page stays open.
Our suggestion: if you want an Audio Overview or study guides from a group of sources, try NotebookLM. If you want to read the PDF itself with your notes beside the text, try Omphalis with one hard source you already know. Check both products' answers against their citations.
Which would I try?
NotebookLM, for study notebooks
Keep NotebookLM (Gemini Notebook) if multi-source Q&A, Audio Overviews, and Studio-style study packs are the whole job. That notebook workflow is real. Omphalis doesn't make overview podcasts.
Try Omphalis with one dense PDF or paper you have been putting off. Read the cleaned page, open an explanation beside a passage, leave a note next to it. If that's the part the notebook was missing, you'll know fast.
Yes. Google renamed NotebookLM to Gemini Notebook in July 2026. People searching either name usually want the same thing: a notebook that answers questions over your sources.
What is a good NotebookLM alternative for reading PDFs with notes beside the text?
Omphalis is a reading app for dense PDFs, papers and articles. A PDF opens as a cleaned reading page. You highlight a passage and your note stays beside it, and opening the mark later takes you back to that passage with the text around it. You can open an explanation beside a hard passage and ask about the source, with citations to the passages used. PDFs are read on paid plans from $9 a month. 30-day trial, no card required. Includes 200 voice minutes, 200 PDF pages and 15 assistant answers a day. On Free, a PDF is kept with its name and page count.
Is Omphalis a NotebookLM alternative?
For some jobs, yes. Both let you ask questions about sources and follow citations. Omphalis is the better fit when you need to finish and understand one hard source: reading it, explanations beside the passage, notes, and narration of the text itself. Keep NotebookLM when Audio Overviews or study guides from several sources are what you need.
Does Omphalis skip the documents for me?
No. Omphalis keeps the full source open for reading, marks, explanations and notes on the passage. A short overview only helps you decide where to start. You still read the piece.
Is Omphalis a knowledge base or a summarizer?
Neither. Omphalis is for recurring work with dense sources that matter. You finish reading them, mark confusing or important passages, keep notes attached to the source, and come back later. Omphalis doesn't try to store everything you have, and it doesn't turn sources into summaries to read instead.
Is listening the same in both products?
No. NotebookLM's Audio Overviews are a discussion or brief about your sources, in formats like Deep Dive, Brief, Critique and Debate. Omphalis reads the source itself aloud in a natural voice, and the page stays open so you can check and mark it.
Can I export my highlights and notes from Omphalis?
Yes. In Settings, Export Your Library writes each item as a Markdown file with its marked passages. Highlights, notes and tags are on every plan, including Free.