What Copilot Can Summarize (Emails, PDFs, Teams Chats, Meetings) and How
The short answer: Copilot summarizes email threads, your inbox, Word documents, PDFs, PowerPoint decks, Excel data, Teams meetings and, with the paid licence, your Teams chats. What changes from format to format is where you ask and which licence you need. Free Copilot Chat works on what you upload or open. The paid licence reads across your mail, chats and files.
Below: the full matrix, the size limits Microsoft actually publishes (fewer than the internet claims), and the prompts I'd use.
The matrix: format, app, licence
Quick naming note: Microsoft 365 Copilot is now called Microsoft Copilot. "Paid" below means that licence. "Free" means the Copilot Chat that comes with a business Microsoft 365 subscription.
1A single email thread
Where: Summary by Copilot (or Summarize) at the top of the thread in Outlook, or the Copilot icon in the toolbar on mobile. The summary has numbered citations that jump to each email. Free: a Summarize button in the reading pane that opens Copilot Chat. Paid: Microsoft's pages suggest Summary by Copilot sits in the paid experience.
2Many emails at once
Where: Copilot Chat in Outlook. Free: questions about your inbox, calendar, meetings and other limited data. Paid: adds your chats and company data. More in my Copilot for Outlook guide.
3Email attachments
Where: in new Outlook, an email with a PDF, PowerPoint or Word attachment offers Summarize a file. The paid "summarize email and attachments in Copilot chat" feature is on iOS and Android only, since Microsoft paused the web, Mac and desktop rollout in April 2026.
4A Word document
Where: the Copilot pane in Word, with the prompt Summarize this document. You get bullets with citations into the document. Free: Basic access in Word, except in large organisations, where unlicensed users lost Copilot in Word on 15 April 2026. Paid: full access.
5A PDF
Where: 4 options. Upload it to Copilot Chat (free or paid). Open it in Edge and select Create a Summary (Edge for Business reads PDFs, not Office documents). Open it in Word, which converts it first. Or in OneDrive on the web, select up to 5 files and choose Summarize this file.
6A PowerPoint deck
Where: Copilot in PowerPoint, prompt Summarize this presentation, then Show key slides or Show action items. Microsoft's 2025 page says it handles decks up to about 40,000 words.
7Excel data
Where: Copilot in Excel. Ask about your data and it answers with charts, PivotTables, summaries, trends or outliers. For a text column (survey comments, say), it can summarize themes and sentiment into a new column, and you hover the superscript number to see the source.
8Teams chats
Paid: with the licence, Copilot can use your work content, including chats, email and files. Microsoft's Outlook support page lists chats as one of the things the paid licence adds, and outside Outlook free Copilot Chat works on the web plus what you upload. Heads-up: from mid to late October 2026, Copilot leaves the Teams chat list and you reach it through the Copilot app.
9Teams meetings
Paid: Copilot during the meeting (private to you) and after it, but after-meeting questions need a transcript. Intelligent recap: Teams Premium or the Copilot licence, and the AI summary needs a transcript in a supported language and a meeting of 5 minutes or more. Recording isn't the requirement. The transcript is. The full breakdown is in my Copilot meetings recap guide.
Size limits: the honest version
1Copilot Chat uploads
Microsoft publishes no upload size, file count or page limit on its support or Learn pages. It just says standard limits apply. The numbers floating around online come from webinars and third-party blogs, so don't plan a process around them.
2Long Word documents
Microsoft said in 2024 that around 80,000 words is a sweet spot for summaries. Today's guidance has no number. It warns that on long files Copilot may focus on the beginning, and that content in the middle gets less attention.
3Questions beat summaries
A question about a single topic usually works on a long document. A summary needs the whole document in context. So on a monster file, ask questions, or summarize it in parts (Microsoft's own advice is to split it).
Summary prompts that work
Summarize this thread in 3 lines: what was decided, what's still open, and who's waiting on me.
Summarize my emails from the last week related to [project or customer name].
Summarize the attached PDF in 5 bullets for my director. Then list every number it quotes, with the page it came from.
What decisions are needed before this document is ready to share?
Review recent email messages and Teams chats. Summarize important updates, direct mentions, and assigned actions in bullet points.
Recap meeting summarizing key takeaways and action items as separate sections, including who's responsible for each.
More per app in my Microsoft 365 Copilot prompt library.
What a summary gets wrong
1It fills gaps
In Word, if the answer isn't in the document, Copilot uses the underlying model's general knowledge. That's how a "summary" ends up with a fact your document never said. Click the citations.
2The middle of long files
See above. And Microsoft admits citations don't always point to later parts of a document.
3What it can't see
Signed, encrypted and IRM-protected emails are out, and so are mailboxes not hosted on Exchange Online. "Nothing urgent" only covers what Copilot could read.
4Same prompt, different answer
Microsoft says it plainly: the same prompt can give different responses. Don't paste a summary into a board pack without reading the source parts that matter.
Need the document in another language rather than shorter? That's translating documents with Copilot.
Questions about Copilot summaries
Can Copilot summarize a PDF?
Yes. Upload it to Copilot Chat, open it in Edge and select Create a Summary, open it in Word, or select it in OneDrive on the web and choose Summarize this file. Copilot Chat can summarize uploaded PDFs with or without the paid licence.
Can Copilot summarize multiple emails at once?
Yes, in Copilot Chat in Outlook. Free users can ask about their inbox, for example emails from the last week about a project. The paid licence adds chats and company data.
Can Copilot summarize a Teams chat?
With the paid Microsoft Copilot licence, yes. Copilot can then use your work content, including chats, email and files. Free Copilot Chat works on the web and what you upload, so plan on the licence for chat summaries.
What is the file size limit for Copilot summaries?
Microsoft publishes no upload size or page limit for Copilot Chat. For long documents, it advises splitting them and summarizing in parts.
Does Copilot need a recording to summarize a Teams meeting?
No, it needs a transcript. After-meeting questions and the intelligent recap AI summary both depend on the transcript. Without a recording, the recap loses the recording, speakers, topics and chapters.
Want your team summarizing in a lunch break?
Summaries are the job I'd pick for a first short live online session, because everyone can try them on their own inbox, documents and meetings right away.