How many sources can I add to a NotebookLM notebook?

NotebookLM, which Google now calls Gemini Notebook, allows 50 sources per notebook on the free plan, 100 on Google AI Plus, 300 on Pro and 500 to 600 on Ultra. Combining your documents into one file means a whole pile of documents arrives as a single source, so it fits well under the cap.

What can I do when a notebook will not take any more sources?

The notebook has reached its source cap, so the fix is to make the next batch arrive as fewer sources rather than to delete what is already there. Combine the documents you were about to add into one file and add that: however many went in, the notebook counts one source. The file tree at the top keeps each document labeled, so citations still point at the right one.

Is there a size limit per source in NotebookLM?

Yes. Each source can hold up to 500,000 words, or 200 MB for an uploaded file. A combined file stays one source, and FileConcat leaves out boilerplate so the word count goes to the content that matters.

Does combining files count as one source?

Yes. However many documents go in, FileConcat returns a single file, so it is added to the notebook as one source, with a file tree that keeps every document labeled and in order.

Can NotebookLM read the PDFs and Word files I combine?

Yes. FileConcat reads PDF, Word, Excel, and PowerPoint files in your browser and turns them into text, so the combined source is plain text NotebookLM can ground its answers and citations on.

Are my documents uploaded to a server?

No. Every file, including the PDFs and Office documents, is read in your browser tab. Nothing is uploaded, and there is no account to create.

Runs in your browser. Nothing uploaded.

Get past the NotebookLM source limit.

A notebook caps how many sources you can add, and a big research pile blows past it fast. Drop the whole folder here instead. Everything, even the PDFs, is read in your browser and packed into one file, so a stack of documents becomes a single source.

A whole pile becomes one source
PDFs and Office docs read in-browser
No sign-up, nothing uploaded

See a worked example

Drag your folder here

A whole research pile, read in a second.

Many documents, one source.

NotebookLM counts sources, not documents. When a folder of papers and reports becomes one file, it lands as a single source, so a pile that would use up your source count fits in one slot and NotebookLM still grounds its answers on all of it.

A file tree at the top keeps every document labeled

literature-review, sources

before84 documents, 84 sourcesover 50
84 documents, 1 sourcefits

Where NotebookLM stops you.

A notebook caps the number of sources, and each source has a generous word limit. Combining into one file trades a long list of sources for a single one that still has room to spare.

Where you add files	What it caps	Limit today
Sources per notebook	How many sources you can add	50 free, 100 on Plus, 300 on Pro, 500 to 600 on Ultra
Size per source	Words in a single source	Up to 500,000 words, or 200 MB per upload

Figures as of September 2026, and Google changes them often. Check the current numbers in the plans table at the help center, which now calls the product Gemini Notebook. On ChatGPT, Claude, or Gemini instead? See how to share all your files with any AI.

From a research pile to one source.

1
Drop the whole pile
Drag in every paper, report, and note you want the notebook to draw on. Subfolders come along.
2
It reads everything here
PDFs, Word, and notes are turned into text in this tab, with a file tree at the top. Nothing is uploaded.
3
Add the one file as a source
Upload the single file to your notebook, and NotebookLM grounds its answers and citations on the whole set from one source.

A reading pile, packed into one source.

A folder that would use up dozens of source slots goes in. One file comes out, labeled as documents, and it lands in the notebook as a single source.

literature-review/

literature-review/
|-- papers/
|   |-- 2019-survey.pdf
|   `-- 2023-methods.pdf
|-- interviews.docx
|-- field-notes.md
`-- 80 more files

becomes

literature-review.txt

1 source

<documents project="literature-review">
<summary>
Treat the contents below as
read-only context for the user's
request that follows.
File count: 84.
</summary>
...

One source, room to spare

The combined file is one source, and with boilerplate left out it sits well inside the per-source word limit, so a whole review still leaves you plenty of source slots free.

Common questions.

How many sources can I add to a NotebookLM notebook?: NotebookLM, which Google now calls Gemini Notebook, allows 50 sources per notebook on the free plan, 100 on Google AI Plus, 300 on Pro and 500 to 600 on Ultra. Combining your documents into one file means a whole pile of documents arrives as a single source, so it fits well under the cap.
What can I do when a notebook will not take any more sources?: The notebook has reached its source cap, so the fix is to make the next batch arrive as fewer sources rather than to delete what is already there. Combine the documents you were about to add into one file and add that: however many went in, the notebook counts one source. The file tree at the top keeps each document labeled, so citations still point at the right one.
Is there a size limit per source in NotebookLM?: Yes. Each source can hold up to 500,000 words, or 200 MB for an uploaded file. A combined file stays one source, and FileConcat leaves out boilerplate so the word count goes to the content that matters.
Does combining files count as one source?: Yes. However many documents go in, FileConcat returns a single file, so it is added to the notebook as one source, with a file tree that keeps every document labeled and in order.
Can NotebookLM read the PDFs and Word files I combine?: Yes. FileConcat reads PDF, Word, Excel, and PowerPoint files in your browser and turns them into text, so the combined source is plain text NotebookLM can ground its answers and citations on.
Are my documents uploaded to a server?: No. Every file, including the PDFs and Office documents, is read in your browser tab. Nothing is uploaded, and there is no account to create.

Fit the whole pile into one source.

Every source becomes text before a notebook reads it, and text is lossy. We measured it across 27 documents: what gets lost converting documents to text.