Microsoft Copilot Notebook Source Limits: Word Count and File Count

You are using Copilot Notebook to summarize or analyze documents, but the output stops short or the tool refuses to process your files. This happens because Copilot Notebook enforces strict limits on how much text it can read from a single source and how many files you can upload in one session. Understanding these limits helps you plan your work and avoid incomplete results. This article explains the exact word count and file count boundaries for Copilot Notebook, how the system enforces them, and what you can do to stay within those limits.

How Copilot Notebook Enforces Source Limits

Copilot Notebook is a feature within Microsoft Copilot that allows you to paste text, upload documents, and then ask questions or generate content based on that material. Unlike the standard chat interface, Notebook is designed for longer, more structured interactions. However, it still operates within technical constraints that prevent it from processing unlimited amounts of text.

The primary limit is a character cap of 60,000 characters per source. This is the total length of the text you paste directly into the Notebook input field or the extracted text from a single uploaded file. The system counts every character including spaces, punctuation, and line breaks. In practical terms, this means a document of about 10,000 to 12,000 words is the maximum for one source. If your file exceeds this, Copilot will either truncate the text silently or refuse to attach it entirely. The exact behavior depends on the file format and how Copilot extracts the text.

The file count limit is separate and simpler. You can attach up to 10 files in a single Notebook session. This includes files uploaded from your device, from OneDrive, or from SharePoint. Once you hit 10 files, the attach button becomes inactive until you remove a file. The combined content of all 10 files must also stay within the overall session context window, which is about 128,000 tokens. Tokens are roughly 4 characters of English text, so the total usable text across all sources is around 512,000 characters. But because the conversation history also consumes tokens, the effective limit is lower when you ask multiple questions.

How Copilot Handles Exceeding the Limits

When you exceed the 60,000-character limit on a single source, Copilot Notebook does not always show an error. Instead, it may process only the first portion of the text. The system uses a sliding window approach: it reads the beginning of the document until it reaches the token limit and ignores the rest. This means your analysis will be incomplete without any warning. For file uploads, the behavior is similar. Copilot extracts text from the file and then applies the same 60,000-character cap. PDFs, Word documents, and text files all go through this extraction process.

Steps to Check and Stay Within the Limits

1. Count the characters in your source text before pasting
   Open your document in a text editor such as Notepad. Select all text and check the character count from the status bar or a word count tool. If the count exceeds 60,000 characters, split the document into smaller sections before pasting into Copilot Notebook.
2. Upload files one at a time and confirm the attachment
   Click the attach paperclip icon in the Copilot Notebook input area. Select a file from your device, OneDrive, or SharePoint. Wait for the file name to appear under the input field. If the file name does not appear, the file likely exceeded the limit or is an unsupported format. Supported formats include .txt, .pdf, .docx, .xlsx, and .pptx.
3. Monitor the file count during your session
   Each attached file shows a small X icon to remove it. Count the visible file tokens. If you reach 10, remove a file before attaching a new one. Alternatively, start a new Notebook session to work with a different set of files.
4. Manage the conversation history to free up tokens
   After several exchanges, the session context window fills up. Click the New Notebook button in the top-left corner to start a fresh session. This clears the history and resets the token count, allowing you to upload new sources or continue analysis from scratch.
5. Use the Copilot Notebook status indicator
   When you type or attach files, look for a small counter next to the notebook icon. Some versions of Copilot show a percentage or token count. If the counter reaches 100 percent, you cannot add more text or files until you clear the session.

If Copilot Notebook Still Refuses Your Files or Text

Copilot Notebook says the file is too large or unsupported

This error appears when the file exceeds the 60,000-character limit after text extraction or when the file format is not supported. Convert the file to plain text (.txt) using a tool like Notepad or Word’s Save As option. Then copy the text and paste it directly into the Notebook input field. If the text is still too long, split it into logical sections such as chapters or sections and paste each part into separate Notebook sessions.

Copilot Notebook stops responding or gives vague answers after a few questions

This indicates that the session context window is full. The system has consumed all available tokens with your source text and previous questions. Start a new Notebook session and paste only the specific section of the document that is relevant to your next question. This keeps the token count low and allows Copilot to generate accurate responses.

Copilot Notebook attaches a file but does not use its content

This occurs when the file contains images, scanned text, or complex formatting that Copilot cannot extract. Use a PDF with selectable text rather than a scanned PDF. For Word documents, save the file as plain text before uploading. If the file is an image with text, use a third-party OCR tool to extract the text and then paste the result into Notebook.

Item	Copilot Notebook	Copilot Chat
Maximum characters per source	60,000 characters	4,000 characters
Maximum files per session	10 files	3 files
Session context window	128,000 tokens	8,000 tokens
Supported file formats	.txt, .pdf, .docx, .xlsx, .pptx	.txt, .pdf, .docx

Understanding these limits lets you plan your work more effectively. Before using Copilot Notebook, check the character count of your source material and split large documents into smaller parts. Keep your session focused on one topic at a time to avoid filling the context window with unrelated history. For long projects, use multiple Notebook sessions and copy the key insights into a separate document. This approach ensures you get complete analysis without hitting the source limits.