What Files Can Claude Read? How to Upload Them
Uploading a file and typing "what do you think?" or "look at this" is the file-upload version of a bare task prompt. Claude has to guess what you actually want from the document, and with a file that guess has more room to go wrong than it does with a short text request, since a single upload can hold dozens of pages of content competing for attention.
Tip
An upload isn't the request. It's context for the request. The question you ask about the file matters as much as the file itself.
What files Claude can read
Claude works directly with documents, spreadsheets, images, and code files, which covers most of what shows up in everyday work: a contract, a budget spreadsheet, a screenshot of an error message, a slide deck exported as a PDF. The upload replaces retyping or describing the content. It doesn't replace telling Claude what to do with it.
| File type | Claude reads it | Best for | Watch out for |
|---|---|---|---|
| PDF (text-based) | Yes | Contracts, reports, papers, exported decks | Very long PDFs compete for attention; ask about one section |
| PDF (scanned or image-only) | Partly | Anything only available as a scan | Text is read from the image and can drop words or numbers |
| Word and text documents | Yes | Drafts, briefs, notes | Tracked changes and comments may not come through |
| Excel and CSV | Yes | Budgets, exports, lists, simple analysis | Upload the file, not a screenshot of it |
| Images and screenshots | Yes | Error messages, charts, UI, handwritten notes | Small or low-contrast text is easy to misread |
| Code files | Yes | Reviewing or explaining a specific file | For a whole repo, use Claude Code instead |
| PowerPoint and Keynote | Partly | Slide text and structure | Export to PDF if the layout or speaker notes matter |
A rough rule for deciding whether to upload something or just describe it in text: if the file is short enough to paste as text in a couple of sentences, typing it directly is often faster. If it's long, has formatting or structure that matters (columns in a spreadsheet, sections in a report), or you'll want to ask several different questions about it, upload it.
| Approach | Use when |
|---|---|
| Paste as text | The content is a few sentences and has no structure that matters |
| Upload the file | It's long, structured, or you'll ask more than one question about it |
| Project knowledge | You'll come back to the same file across many separate conversations |
A process for getting a real answer out of a file
- 1
Upload the file before you ask anything
Attach the document first, then write your question in the same message or the next one. Claude needs the file in context before a specific question about it makes sense.
- 2
Ask one specific question, not a general one
"What does this say about the return policy?" gets a usable answer. "What do you think of this?" gets a generic reaction, since Claude has no way to know what aspect you actually care about.
- 3
Reference a specific part when you have one in mind
If you already know roughly where the relevant content is, a page number, a section heading, a rough location, say so. It narrows what Claude focuses on and reduces the chance of an answer built from the wrong part of the file.
- 4
Ask a targeted follow-up instead of a second full read
Once you have an answer, a follow-up question about the same file reuses the context Claude already has. There's no need to re-upload or re-explain what the document is.
Here's our vendor agreement. Find the section on termination and tell me how much notice either side has to give, quoting the exact sentence.
”That question names a specific section and a specific piece of information to extract. A version that just said "review this contract" would get back a broad summary instead, which is a reasonable answer to a broad question but not the one you actually needed.
The file is uploaded before the question is asked
The question names a specific piece of information, not a general reaction
A page, section, or rough location is included if you already have one in mind
Follow-up questions build on the same conversation instead of re-uploading
Inside Claude Tutorial
The same specific-question habit applies to every file type.
Whether it's a contract, a spreadsheet, or a screenshot, the skill that makes an upload useful is the same one taught throughout the app: ask for something specific, not a general reaction.
Asking multiple questions about the same file
A single upload can support several different questions across a conversation, and that's usually more efficient than re-uploading for each one. After the first specific question, a follow-up can ask about a different part of the same document without restating what the file is.
Now check the same contract for any clause about automatic renewal, and tell me how far in advance we'd need to cancel to avoid it renewing.
”Each question stays specific, and each one builds on a file Claude already has open. That's a different pattern than starting over with a new upload and a new generic prompt each time, and it's noticeably faster once a document needs more than one pass.
Common mistake
Uploading a file and asking a question so broad it could apply to any document. "Summarize this" works, but it produces the same kind of flat, generic overview no matter what the file actually contains. A specific question gets a specific answer.
When the file doesn't behave the way you expect
Not every file uploads cleanly. An image-heavy PDF, a scanned document, or a spreadsheet with unusual formatting can sometimes come through with less readable content than a clean text file would. If an answer seems to be missing something you know is in the document, that's usually the first thing worth checking, not a sign the question was wrong. Working With PDFs and Long Documents in Claude covers this in more detail, including what a scanned document looks like from Claude's side and what to do about it.
Common mistakes
- Uploading a screenshot of a spreadsheet instead of the file. Claude can read the picture, but it can't sort, total, or filter it. Upload the actual
.xlsxor.csv. - Attaching a 200-page document when you need two pages. The relevant detail competes with everything else for attention. Upload the whole thing if you must, but point Claude at the section.
- Asking before the upload finishes. If the file isn't fully attached when you send, Claude answers from the text alone. Wait for it to appear, then ask.
- Assuming a scanned PDF was read perfectly. Text pulled from an image can drop a digit or a "not." Spot-check any number or clause that matters.
Frequently asked questions
What file types can Claude read?
PDFs, Word and plain-text documents, Excel and CSV spreadsheets, images and screenshots, and code files. PowerPoint and scanned PDFs work partially; export slides to PDF and expect some text loss on scans.
Can Claude read PDFs?
Yes. Text-based PDFs come through cleanly. Scanned or image-only PDFs are read from the image, so words and numbers can occasionally drop, and it's worth checking anything important.
Can Claude read Excel spreadsheets?
Yes. Upload the .xlsx or .csv file rather than a screenshot, so Claude can work with the actual rows and columns instead of a picture of them.
Can Claude analyze images and screenshots?
Yes. It can read an error message, describe a chart, pull text out of a photo, or comment on a UI. Small or low-contrast text is the main thing it misreads.
How many files can I upload at once?
More than one, which is what makes side-by-side comparison possible. The exact limit and maximum file size change over time, so check the current limits in the app if you're near them.
Can Claude read a scanned document?
Partly. It reads the text off the image rather than from a text layer, so accuracy drops on faint scans, handwriting, and dense tables. Verify key details against the original.
Continue reading
- Working With PDFs and Long Documents in Claude: the specific issues that come up with PDFs and very long uploads, and how to work around them.
- Comparing Multiple Documents Side by Side: asking one structured question across more than one uploaded file at a time.
- Claude Projects: Context That Sticks Around: where to keep a file you'll come back to across many separate conversations.