Can NotebookLM read XLSX files?

No. Gemini Notebook does not accept XLSX or XLS files. Convert the spreadsheet to PDF or CSV first, or use the Drive picker to add a Google Sheets version if your data is already in Google Sheets.

Which format is better for spreadsheet data in NotebookLM: PDF or CSV?

CSV works well for clean numerical data with clear column headers, because it produces plain text the notebook reads reliably. PDF is better when the visual layout is important or when the spreadsheet has complex formatting that would be lost in a CSV export.

Why does NotebookLM misread my spreadsheet columns?

Column misreading usually comes from a damaged header row, merged cells, or inconsistent column counts after export. Open the converted file before uploading, check that headers are on a single row, and ask the notebook to describe the data structure as a verification step.

Can I upload multiple sheets from one Excel workbook?

Not as a single file. Export each sheet separately as PDF or CSV and add each as a separate source. Alternatively, combine the relevant data into a single sheet before exporting.

How does fenbs help with spreadsheet analysis in NotebookLM?

fenbs keeps a record of which version of the spreadsheet you used, the format it was converted to, and the key findings from the analysis. If the project continues in a later session or in a different AI app, those decisions are available without re-importing and re-explaining the data.

NotebookLM XLSX Files: Prepare Spreadsheet Sources

Gemini Notebook (formerly NotebookLM) does not accept XLSX files directly. Here is how to convert a spreadsheet to a supported format, what to check before uploading, and how to verify that labels and values came through correctly.

August 11, 2026Updated October 21, 20264 min read

Gemini Notebook, the current name for NotebookLM since July 2026, does not accept XLSX or XLS spreadsheet files directly. To use spreadsheet data as a source, you need to convert the file to a supported format first—typically a PDF or a plain text file. Tools like fenbs can keep a record of the source references, conversion decisions and analysis notes so the work persists across sessions.

For related source format questions, see /blog/notebooklm-alternatives and /blog/claude-projects-vs-notebooklm. For file size limits, check the Gemini Notebook help page directly.

What file formats Gemini Notebook accepts instead of XLSX

Gemini Notebook accepts PDFs, plain text files, Google Docs, Google Sheets (via the Drive picker, not file upload), web URLs, YouTube links and audio files. For spreadsheet data, the most practical paths are converting the XLSX to PDF, converting it to CSV, or uploading the Google Sheets version via the Drive picker if your data is already in Google Sheets.

PDF export preserves the visual layout of the spreadsheet but creates problems for tables with many columns—wide tables often get truncated or wrapped in ways that obscure column relationships. CSV export produces clean, readable text that the notebook handles well, but loses any formatting, formulas or charts.

How to export a spreadsheet in a supported format

In Excel: open the file, choose File, Save As or Export, and select either PDF or CSV (comma-separated values) as the format. In Google Sheets: choose File, Download, and select PDF or CSV. For multi-sheet workbooks, both formats typically export only the active sheet; repeat the export for each sheet you want to add as a source.

If you are converting to CSV, check that the column separator is a comma, not a semicolon or tab, since some regional Excel settings default to semicolons. Gemini Notebook handles standard CSV well; non-standard separators may produce a source that looks like a single long column.

PDF export: best when visual layout matters or when the notebook needs to see the table as a human would read it.
CSV export: best for clean numerical data where the relationship between columns is clear from the headers.
Google Sheets via Drive picker: most direct if your spreadsheet is already in Google Sheets; avoids a format conversion step.
Avoid copying raw spreadsheet data into a text file without structure: the notebook needs column headers and consistent rows to reason correctly about the data.

What to check before uploading

Before uploading, open the converted file and verify it looks like you expect. A PDF of a wide spreadsheet should show readable column headers and values. A CSV should have consistent column counts on each row and no mangled special characters from the export.

Check for merged cells in the original spreadsheet. Merged cells create problems in both PDF and CSV exports: the cell content may appear only once, which makes the row structure confusing when the notebook tries to read it. Unmerge cells and replace merged headers with repeated values before exporting.

How fenbs helps

Record which version of the spreadsheet you used

After uploading a converted spreadsheet to Gemini Notebook, save the source reference and the conversion decision—which format, which sheet, any cleaning steps—to your project in fenbs. If the analysis is challenged later, you have a clear record of what data was used.

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Common problems when tables arrive in Gemini Notebook

Even a well-prepared export can have problems inside the notebook. The most common are column headers that were truncated in the export, numerical values that lost their units, and multi-line cells that split across what the notebook reads as separate rows. After uploading, ask the notebook to describe the structure of the data—number of columns, what each column header says—and compare that description against what you expect.

If the notebook misidentifies column relationships, it will produce wrong analysis. For example, if a header row did not transfer cleanly, the notebook may treat the first data row as the headers. Catch this before asking substantive analysis questions.

For spreadsheets with formulas, pivot tables or conditional formatting, the conversion will lose that logic entirely. The notebook sees only the values that were displayed, not the calculations behind them. If the analysis depends on understanding how values were derived, include a short plain-text explanation of the formula logic as a separate text source alongside the data.

How to do this with fenbs

fenbs does not connect to Gemini Notebook or store spreadsheet files. It keeps the source references and analysis decisions that your spreadsheet work produces, available to any AI app you use in a future session.

Create a free account and open or add the project this spreadsheet analysis belongs to.
After uploading the converted file, add it to the project's Links and listings with a note on the format used and any cleaning steps applied.
When the notebook's analysis leads to a key finding, record it as a context note or a Decision so future sessions start with that confirmed result.
If you later update the spreadsheet data, note the change in the project so the next session knows which version of the data was analyzed.
Connect Claude, ChatGPT or another AI from Integrations to read the project context and continue the analysis without repeating the setup.