Microsoft 365 Copilot + SharePoint

How to stay uptodate about the size limitation topic:

The MS support article "Keep it short and simple" is the official page to stay uptodate about changes regarding document size limitation: Keep it short and sweet: a guide on the length of documents that you provide to Copilot - Microsoft Support

The article is also good to understand how Copilot handles files which are larger than the current limitations. 

Since M365 Copilot works with data on MS Graph, which means search plays a role in here. Therefore I would keep an eye on this article related to search limitations too: Search limits for SharePoint - SharePoint in Microsoft 365 | Microsoft Learn

What you could do now:

I would build an agent to handle sumarizing and analyse of the larger files.

Here there are limitations to keep an eye on, too:

For OneDrive: Quotas and limits - Microsoft Copilot Studio | Microsoft Learn

For SharePoint: Quotas and limits - Microsoft Copilot Studio | Microsoft Learn

Short answer:

• Yes—Microsoft is working to expand what Copilot can handle
• Combining outputs across files is possible today

There isn’t a single, official MB limit published across all Copilot surfaces. In practice, chat uploads do throw size errors (like the 150 MB message you saw). Microsoft’s public stance is to watch content length (e.g., up to ~300 pages / ~1.5 M words for full‑document summarization) and they’ll raise limits over time—just no date yet.

Practical ways to get what you need today
1) One combined summary for a handful of files (fast)

In OneDrive on the web, select up to 5 files → Copilot ▸ Summarize for a single, consolidated summary panel you can iterate on (“compare positions,” “list contradictions with citations,” etc.).

2) Cross‑document synthesis at site/library scale

Use SharePoint agents (built into SharePoint). Create an agent scoped to your matter site, library, or a set of folders/files. Then ask for a single issues list, timeline, or executive brief across everything you’re allowed to see. This is the best option for large matters.
FYI on limits: when agents read from SharePoint, enhanced search supports files up to ~200 MB per item; when you upload files to an agent as knowledge sources, the per‑file cap is 512 MB. That helps some big files—but not multi‑GB PDFs.

3) Copilot Notebooks for a single, combined deliverable

Copilot Notebooks let you collect references (SharePoint/OneDrive files, chats, pages) and ask Copilot for one consolidated output (e.g., “Create an executive summary with sections: Background, Claims, Key Facts, Procedural History, Open Issues.
Notebooks are great for ongoing matters (you can keep adding references) and keep Copilot’s answers scoped to your notebook. They do not bypass file‑ingestion caps; they just help you combine and structure results.

4) Work a single large document without chat‑upload limits

Open (transform) the file in Word and use Copilot side‑by‑side; Copilot can reason over the open document (often avoids the chat upload gate). Still follow the length guidance for best results.

For very large legal files (500 MB–2 GB)

Pre‑process before AI: OCR scanned PDFs, remove unnecessary images, or split by logical sections (exhibits, transcript days, motion/response/reply). Then use SharePoint agents or Notebooks for the combined brief and Word + Copilot to polish. (This aligns with Microsoft’s guidance that results are more accurate when the model can access the full relevant context.)

Although the limits mentioned by pradejain​ (150 MB/file and a single summary per file) are confirmed by Copilot itself if you ask the question, there is an alternative.

You can set up a custom built agent in SharePoint by specifying the site or library where your files are located.

You can then ask the agent about the content of EVERYTHING in the repository. It won't generate a document-style report, but it will give you text-based answers that will make it reasonably easy for you to put together your own document of conclusions.

Translated with https://www.deepl.com/?utm_campaign=product&utm_source=web_translator&utm_medium=web&utm_content=copy_free_translation (free version)

Hi mcheatham​ 

1. The 150 MB file size limit Right now, Copilot won’t process files bigger than about 150 MB in the chat experience. That’s a hard limit in the current design, and it’s there because of how Copilot breaks content into chunks for the AI to read. Microsoft has said they’re working to expand Copilot’s capabilities over time, so bigger files should be possible in the future — but there’s no confirmed date yet.
2. Multiple files = multiple summaries If you upload several files at once, Copilot will give you a separate summary for each one. It doesn’t yet combine them into a single, merged summary. This is something a lot of people have asked for, and Microsoft has acknowledged the feedback, so it’s on their radar.

What you can do in the meantime

• For large files: split them into smaller sections (by chapter, heading, or logical break) before sending them to Copilot, then stitch the summaries together.
• For multiple files: merge the relevant parts into one document under 150 MB, then run that through Copilot for a single summary.
• Or, instead of uploading, use Copilot inside Word, Excel, or PowerPoint to ask targeted questions about the content stored in SharePoint — sometimes that’s faster than summarizing the whole thing.