According to XDA-Developers, Google’s NotebookLM appears to be quietly testing a Deep Research feature that users have been spotting since late March 2025. The feature was first noticed by Reddit user u/Moist_Emu6168, who shared a screenshot showing new toggles for Web and Fast Research options. TestingCatalog had actually predicted this back in August 2024, mentioning that NotebookLM would soon pull sources from both the web and Google Drive. The Deep Research capability represents a significant shift from NotebookLM’s current source-grounded approach, where everything is tied to materials users manually upload. This comes just days after Google announced conversation history saving, addressing another major user complaint. The feature seems to be rolling out gradually, with users in India and elsewhere confirming they’re seeing it too.
Why this changes everything
Here’s the thing: NotebookLM has always been amazing at working with documents you give it, but it’s been completely blind to anything outside your uploaded materials. That’s been its biggest strength and weakness. You get perfect accuracy with your own sources, but you’re limited to what you’ve already found. Now with Deep Research, it’s like giving your research assistant the ability to hit the library and find new materials on its own.
And honestly, this is exactly what NotebookLM needed to compete with other AI research tools. I’ve been manually using Gemini’s Deep Research feature alongside NotebookLM because they complement each other so well. Gemini finds the information, NotebookLM helps me organize and understand it. Having both capabilities in one tool? That’s a game-changer for anyone doing serious research work.
The elephant in the room
But here’s my big concern: hallucinations. The reason I love NotebookLM is that it’s so reliable because it’s tied directly to my sources. Once you start pulling from the wild west of the internet, accuracy becomes a real question. Will Google maintain that same focus on verifiable sources when it’s crawling the web?
Looking at the Reddit discussion, other users are wondering the same thing. The feature appears to have both “Fast Research” and “Deep Research” modes, which suggests Google might be thinking about this too. Fast Research could give you quick answers while Deep Research does the thorough, source-verified deep dive.
Where this puts NotebookLM
Basically, this move positions NotebookLM as a much more complete research platform. Before, it was amazing for analyzing existing materials but limited for discovery. Now it can do both. That puts it in direct competition with tools like Perplexity AI and even some of Google’s own products.
The timing is interesting too. According to TestingCatalog’s earlier reporting, this has been in the works for months. Google’s clearly been methodical about this rollout, which makes sense given the potential for things to go wrong with web-sourced content.
So what’s next? If Google can pull this off without sacrificing NotebookLM’s signature reliability, they might just have created the ultimate AI research assistant. But that’s a big if. For researchers and professionals who need both comprehensive discovery and accurate analysis, this could become an indispensable tool. The key will be whether Google can maintain that source-grounded integrity while expanding its capabilities.
