Question 1

Does Google NotebookLM have captions or subtitles?

Accepted Answer

No. Google NotebookLM ships no closed captions and no timed text track for Video Overviews or Audio Overviews. LM Subs generates captions in your browser from the audio-only stream and renders them inside the player, with export to SRT, VTT, TXT, MD, CSV, and JSON.

Question 2

Is LM Subs free to use?

Accepted Answer

The extension is free and MIT licensed. You bring your own speech-to-text API key, and the two recommended providers, Groq and Mistral, both offer permanent free tiers with no credit card. You can also point LM Subs at a local Whisper server and pay nothing.

Question 3

Does LM Subs upload my NotebookLM videos anywhere?

Accepted Answer

No. Audio extraction happens entirely in the browser, and only the compact audio track is sent to the provider whose key you entered. Captions stay in local browser storage unless you sign in and turn on encrypted sync.

Question 4

Can I get captions for NotebookLM Audio Overview podcasts?

Accepted Answer

Yes. LM Subs detects Audio Overview audio elements, including detached players inside shadow DOM, and renders captions in a caption dock with both host labels preserved.

Question 5

Who created LM Subs?

Accepted Answer

LM Subs was created by Sarang, known online as @sarang-cmd, a computer science student and agentic engineer based in Germany. The project is open source under the MIT license at github.com/sarang-cmd/lm-subs and is not affiliated with Google LLC.