Files & long context

Claude becomes far more useful when it works with your material. You can upload files directly into a chat or add them as Project knowledge.

What you can upload

• Documents: PDF, Word, text, Markdown.
• Spreadsheets & data: Excel, CSV.
• Images: screenshots, photos, charts, diagrams (Claude can see and interpret images).
• Slides: PowerPoint.
• Code: source files.

Claude reads the content and can summarize, analyze, extract, compare, rewrite, or answer questions about it.

The superpower: a huge context window

Modern Claude models have a very large context window: up to around 1 million tokens (roughly a few thousand pages). In practice that means you can give Claude a whole report, a long contract, or a big transcript and ask questions across all of it at once.

Here are three vendor contracts (attached). 
Build a comparison table: payment terms, termination clause,
liability cap, and any unusual conditions. Flag anything risky.

Working well with long documents

• Put your instructions first, the document last. Claude follows leading instructions more reliably. (Anatomy.)
• Delimit the material. Wrap pasted text in tags or fences so Claude separates your ask from the content.
• Ask for citations/anchors. "Quote the exact sentence that supports each point" makes answers verifiable.
• Be specific about scope. "Focus only on section 4" beats "tell me about this."

Images count too

Claude accepts images as input. Useful moves:

Here's a screenshot of an error message. What does it mean
and how do I fix it?

This is a photo of a whiteboard from our meeting.
Turn it into a clean, typed action-item list.

A note on cost and limits

Large files use more of your usage budget, because Claude re-reads the relevant context. Tips:

• Upload only the pages/sheets you actually need.
• For repeated work on the same big document, put it in a Project so you're not re-uploading it every chat.
• Builders can use prompt caching to make repeated large contexts cheaper (see Choosing a model.

Sensitive data

Be thoughtful about uploading confidential or personal data. Check your plan's data handling and your organization's policies first. See Privacy & data.

Next: how memory carries useful context across chats.