KastorFlowUpdated November 6, 2026
NotebookLM extensions compared, feature by feature
Extensions for NotebookLM, now Gemini Notebook. We make KastorFlow; the other extensions' features are taken from their own sites and store listings.
Most NotebookLM extensions do one job: folders, imports, YouTube or flashcards. KastorFlow does those jobs and adds what no other extension here lists: it audits a notebook's sources, fills the gaps with sources you approve, builds a research notebook from a topic and repeats all three on a schedule. It also runs automations and connects to Obsidian, Readwise and Anki.
Feature by feature
| Feature | KastorFlow | Kortex | NotebookLM Tools |
|---|---|---|---|
| Audit a notebook: score every source, flag weak ones, show missing kinds | Yes | — | — |
| Fill the gaps with sources you approve | Yes | — | — |
| Build a research notebook from a topic (preview every source on Pro) | Yes | — | — |
| Build, audit and fill gaps on a schedule | Yes | — | — |
| Automations | 10 triggers, 16 actions | 8 triggers, 11 actions | Studio runs after the usage reset |
| Obsidian, both ways | Yes | Markdown export for it | — |
| Readwise, Slack, Discord | Yes | — | — |
| Flashcards straight into an Anki deck | Yes | — | A CSV to import |
| Library map of every notebook, knowledge graph of each | Yes | — | — |
| Find duplicates, delete sources in bulk across notebooks | Yes | — | Merges sources |
| Check the notebook has room before importing | Yes | — | — |
| A video's slides captured beside its transcript | Yes | — | — |
— means the extension's own site doesn't mention it (kortex-notebooklm.com and nlmtools.com, read October 22, 2026), not that it can't be done. One to one: KastorFlow vs Kortex · KastorFlow vs NotebookLM Tools · KastorFlow vs NotebookLM Web Importer · KastorFlow vs ExtendLM · KastorFlow vs YouTube to NotebookLM
Folders and organizing
Gemini Notebook now groups notebooks into collections and can label the sources inside a notebook by topic. It still has no folders for sources across notebooks. Folders in Gemini Notebook
| Extension | What it does |
|---|---|
| KastorFlow | Collections of notebooks, folders of sources from any notebook, tags, a library map of every notebook, search across all of them |
| FolderLM | Folders for notebooks, bulk import, merging, prompts |
| Notebook LM Folders | Folders for notebooks, colors, pins |
| Gemini Notebook Organizer | Nested folders and tags on notebooks |
| NotebookLM Organizer | Color tags on notebooks |
| NoteShelf | Folders and subfolders for notebooks |
Importing many sources
Gemini Notebook takes several links at once, separated by a space or a new line. Import many sources at once
| Extension | What it does |
|---|---|
| KastorFlow | Many links in one run, a CSV of links, open tabs, an RSS or Atom feed, several files; checks the notebook has room first |
| NotebookLM Web Importer | Pages in one click; link lists, open tabs, feeds |
| FolderLM | Bulk import alongside its folders |
YouTube
Gemini Notebook takes links to single public videos, not playlists or channels. YouTube to Gemini Notebook · KastorFlow vs YouTube to NotebookLM
| Extension | What it does |
|---|---|
| KastorFlow | One source per video from a playlist, channel or search; a whole playlist merged into one source; a video's slides captured beside its transcript |
| YouTube to NotebookLM | Videos, playlists, channels and search results |
| NotebookLM Web Importer | Videos and playlists |
Duplicate sources
| Extension | What it does |
|---|---|
| KastorFlow | Finds duplicates beside the source list, then deletes the sources you pick, in one notebook or across all of them |
| NotebookLM Deduper | Finds copies by title in the open notebook |
Flashcards to Anki
Gemini Notebook makes flashcards in Studio but doesn't send them to Anki. NotebookLM flashcards to Anki
| Extension | What it does |
|---|---|
| KastorFlow | Sends flashcards straight into an Anki deck, and connects Obsidian and Readwise too |
| Study Cycle Bridge | Sends the flashcards you pick into Anki |
| AnkiNLM | A CSV of flashcards to import into Anki yourself |
| Flashcards Converter | Turns a flashcard CSV into an Anki package on its own server |
How we compared
- Each extension's features come from its own Chrome Web Store listing; Kortex's and NotebookLM Tools' from their own sites. All read October 22, 2026.
- "—" means we found no mention of the feature there, not that it can't be done.
- We make KastorFlow. Spotted something wrong or out of date? Tell us and we'll fix it.
Audit your sources, fill the gaps and keep every notebook current. Free to install, no account needed to start.
Add to ChromeQuestions
What is the best NotebookLM extension?
Most NotebookLM extensions do one job: folders, imports, YouTube or flashcards. KastorFlow does those jobs and adds what no other extension here lists: it audits a notebook's sources, fills the gaps with sources you approve, builds a research notebook from a topic and repeats all three on a schedule. It also runs automations and connects to Obsidian, Readwise and Anki.
Which NotebookLM extension checks the quality of my sources?
KastorFlow. Its audit scores every source in a notebook, flags the weak ones and shows which kinds are missing: authority, academic, community, recent and practitioner sources. Enrich then adds sources for the gaps, only after you approve them. The audit
Is there a free NotebookLM extension?
Yes. KastorFlow is free to install, with no account needed to start. Its free plan includes the library map, search across every notebook, tags, up to 10 folders, finding duplicates and deleting sources in bulk, 5 research notebook builds a month and 3 YouTube playlist runs a month.
Do NotebookLM extensions work with Gemini Notebook?
Gemini Notebook is NotebookLM's name since July 16, 2026. KastorFlow works on both notebook.google.com and notebooklm.google.com. Check each extension's listing: several still mention only NotebookLM.