NotebookLM is no longer just a place to dump your notes. Google has added a feature called “Discover sources” that lets the AI assistant proactively search the web, select relevant content, and summarize it — all based on a user’s prompt.
The company announced the update on April 2, positioning it as part of a broader effort to make the tool more dynamic and research-capable.
Users can now describe a topic, and NotebookLM will search online materials, analyze them, and return up to ten suggested sources, each with an AI-generated summary. These recommendations appear in the “Sources” panel of each notebook, where users can review and choose what to include. According to Google, “You can then add these sources to your notebooks, expanding your research and building more comprehensive notebooks.”
This feature rolls out alongside enhanced PDF comprehension, which allows NotebookLM to interpret embedded graphs and images in addition to plain text—an essential improvement for users working with technical or scientific material. Audio Overviews, another core feature of the platform, remain limited to English output, though source material in more than 35 languages is supported.
Curiosity Mode and New Input Formats
NotebookLM now includes an “I’m Feeling Curious” button, which surfaces sources on random topics for spontaneous exploration. This feature mirrors Wikipedia’s “random article” concept but uses generative AI to deliver contextually linked and summarized documents for users to explore and learn from.
File format support has also expanded. Users can upload Google Slides, YouTube videos, audio files, and web URLs in addition to PDFs, Google Docs, and plain text files. NotebookLM can process YouTube transcripts—including autogenerated ones—and produce summary takeaways. These enhancements build on capabilities introduced in late 2024 when Google first enabled AI-powered summaries of audio and video sources.
This functionality feeds directly into the platform’s Audio Overview tool, a podcast-style summary generator first launched in September 2024. The tool has since evolved with options to customize AI voice style, focus, and even persona. NotebookLM’s Audio Overview tool enables users to convert uploaded content — including Google Docs, PDFs, and YouTube videos — into interactive AI-generated audio conversations.
NotebookLM’s Expansion From Pilot to Premium Plan
Originally introduced as Project Tailwind during Google I/O 2023, NotebookLM began as a niche research assistant, evolving into a widely used tool. It took a more serious turn with the release of NotebookLM Plus in December 2024, aimed at enterprise and academic teams. This version introduced shared notebooks, role-based access, larger capacity limits, and a redesigned three-panel layout for sources, chat, and document generation.
NotebookLM Plus later became available to individual users through its individual rollout in February 2025 via the $19.99/month Google One AI Premium plan. That move brought high-end features to a much broader audience, including students and freelance professionals.
New additions like analytics dashboards, custom AI personas, and shareable chat notebooks further blurred the lines between enterprise and personal research workflows. These premium features helped position NotebookLM not only as a note-taking companion but as a standalone AI research suite.
Mind Maps and Visual Learning Tools
March 2025 saw the rollout of Mind Maps, a feature that turns raw notes into interactive visual diagrams. Users can explore complex topics through expandable nodes, helping them grasp structure and relationships across ideas. These visualizations are especially useful for learners who benefit from spatial organization of information and help reduce the friction of juggling multiple documents or strands of research.
NotebookLM’s Gemini-powered backend supports these visual and linguistic tasks. The tool taps into Google’s evolving LLM stack to offer multi-language input support, personalization, and media comprehension. Gemini’s ability to draw on prior user activity and search history plays a role in tailoring responses, though Google hasn’t confirmed which version of Gemini is currently powering Mind Maps or Discover sources.
AI Competition and Changing Leadership
NotebookLM’s expansion highlights Google’s broader strategy in the competitive AI workspace. While Microsoft embeds Copilot directly into its productivity apps, Google has opted for a modular and standalone approach. This separation allows NotebookLM to develop as a flexible workspace for both structured collaboration and open-ended research.
Rival products like NotebookLlama from Meta and the open-source Open NotebookLM offer greater transparency and customization, but lack features such as team collaboration, media processing, and advanced analytics. A leaked Google memo from 2023 acknowledged the rapid growth of open-source AI, prompting renewed investment in differentiated features like those found in NotebookLM.
Internally, Google is also shifting leadership in its AI division. As The Verge recently reported, Sissie Hsaio is stepping down as head of the Gemini app, with NotebookLM creator Josh Woodward taking over. This change could further align product development between Google’s note-based AI assistants and its broader generative AI strategy.
Some Unanswered Questions
While the Discover sources feature offers substantial benefits, it also introduces new variables. The system’s criteria for ranking or filtering suggested content have not been disclosed. That makes it harder to assess the reliability of these AI-generated suggestions, especially for academic or policy-related research. Though users have control over which sources to import, the absence of transparency about how the results are ranked may affect trust.
Another area to watch is privacy. Business-tier users benefit from client-managed encryption and team-based permissions, but Google has not made it clear whether these protections extend to Google One subscribers. For a tool that now ingests documents, media, and web content, security will likely become a more visible part of the product discussion going forward.
Still, NotebookLM’s evolution suggests it is becoming more than a note-taker. With new tools for discovering, organizing, and summarizing information, it increasingly resembles a collaborative analyst — one that not only listens and reads, but also finds what you might have missed.
