KastorFlow vs Kortex

Feature by feature

Kortex's features as listed on kortex-notebooklm.com and its features page, read November 6, 2026. — means they don't mention it, not that it can't be done. The KastorFlow column is checked against the extension itself. Spotted something out of date? Tell us and we'll fix it.

What Gemini Notebook now does without either

Before you compare extensions, check what Gemini Notebook does on its own. Two features we tested on November 6, 2026 cover part of what organizing extensions were for.

Auto-label sources by topic is a button above the source list. In a fresh test notebook, one click sorted our 8 sources into labelled groups, such as Neural Networks and Datasets, in about 8 seconds. You can rename or remove a label, and removing one keeps its sources.

Collections on the home page group notebooks, like folders: name one, then tick the notebooks to add. So for simple grouping you may not need an extension. What Gemini Notebook still didn't do in our test: tag sources across notebooks, delete several sources together, catch a link added twice, refresh a web page or YouTube source, or run anything on its own.

What the differences mean in practice

An audit tells you which sources to trust

Gemini Notebook doesn't rate sources. KastorFlow's audit checks each source two ways. It scores how relevant and how authoritative the source is for the notebook's topic, and it flags broken, cut-off or cluttered text with a score from 0 to 10, where under 6 is worth cleaning. It also rates five kinds of source, authority, academic, community, recent and practitioner, as strong, good, thin or missing. That helps once a notebook has grown past what you remember adding.

Enrich then finds sources for each gap. Nothing goes in until you tick it, and never more than the notebook has room for. Free and Pro include 1 audit and 1 enrich a month; Pro+ has no monthly limit. How the audit works

A playlist as one source saves room

A free notebook holds 50 sources, and a 40-video course added video by video fills 40 of them. KastorFlow can merge a playlist or a channel's recent uploads into one source, one for every 100 videos, which leaves 49 slots for papers and notes. The trade-off: you can't tick single videos inside a merged source. Free includes 1 merge a month, with a free sign-in; Pro includes 50. A playlist as one source

Automations: similar size, different triggers

Both react to tags, new sources, a finished Audio Overview and a finished podcast episode. KastorFlow's rules can also start on a schedule, or when an audit, a research build, a YouTube import or a Readwise sync finishes. Kortex's can start when a notebook moves to a collection, a title contains your text or a notebook reaches a number of sources. KastorFlow's automations are on Pro; notebook autopilot, which builds, audits and enriches on a schedule, is on Pro+. Automations

Notes, highlights and flashcards

Kortex exports Markdown that Obsidian can open. KastorFlow's Obsidian connection goes both ways: vault notes come in as sources, and answers go back with their citations. Readwise, Slack and Discord connect too. All four connections are on Pro+. Gemini Notebook made 52 flashcards from one 18-minute video in our test but offered no export; KastorFlow sends a set straight into an Anki deck. Free includes 1 send a month.

Kortex's site also lists two things KastorFlow doesn't do: a crawler that follows links out from one page, and routing links to notebooks by their web address.

Try KastorFlow next to Kortex

You don't have to switch to compare them. KastorFlow works on the same Gemini Notebook tabs and Google account, and reads the notebooks already there. Nothing needs moving.

1. Add KastorFlow to Chrome. No account is needed to start.
2. Audit a notebook you know well. In KastorFlow, open Research & improve → Audit and enrich, choose the notebook and run the audit. See whether the flagged sources are the ones you would have dropped.
3. Try a playlist as one source. Open a YouTube playlist, click the KastorFlow icon in Chrome's toolbar, choose Import playlist as one source and pick the notebook. It checks the notebook has room before it starts.

• KastorFlow keeps its own tags, folders and collections. It doesn't change Gemini Notebook's labels or Collections, or anything Kortex has saved.
• Both can add buttons to the Gemini Notebook page. If something looks off, turn one off for a minute at chrome://extensions to see which it is.
• The library map and search across notebooks are free for 7 days, then need a free KastorFlow account.
• If you remove KastorFlow, your notebooks and the sources it added stay in Gemini Notebook.

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