What is the actual file size limit?

As of June 2026, 500 MB per file for chat uploads, with up to 20 files per chat. The 30 MB limit applies to files added to a Project, not chat uploads. Images can be up to 8000x8000 pixels.

Why does my small PDF still get stuck?

Almost always page count. Claude does full visual analysis only on PDFs under 100 pages; a small but long PDF stalls or returns `A maximum of 100 PDF pages may be provided.` Split it under 100 pages.

How long should processing take?

A few seconds for images, up to about a minute for a normal PDF. If it is longer than that and a small control file is fine, the specific file is the problem.

Does Claude OCR scanned PDFs?

Yes, but quality depends on the scan, and the 100-page visual limit still applies. Clean text PDFs are always faster.

Where do uploaded files live?

They are attached to the conversation. Deleting the chat removes access to the file.

Troubleshooting

Claude File Upload Stuck on Processing: Fix It Fast

Claude shows the spinner forever and the file never attaches. The usual culprit is a PDF over 100 pages or a browser extension breaking the upload — here is how to tell which one and fix it.

Published: May 23, 2026 Updated: Jun 15, 2026 Author: AI Productivity Guide Team 🌐 查看中文版本

You drag a PDF into Claude, paste an image, or click the paperclip and pick a file. The thumbnail appears with a “Processing…” label and a spinner. Minutes later it is still there. Sending the message does nothing because the file never finishes processing, so it cannot be attached to the prompt.

Fastest fix: if it is a PDF, check the page count first, not the file size. As of June 2026 Claude.ai accepts files up to 500 MB each in chat, but it only does full visual analysis on PDFs under 100 pages. A 200-page, 20 MB PDF is well under the size cap yet stalls or errors on the page limit. Split it to under 100 pages (or copy the relevant text straight into the chat) and the upload completes in seconds. If it is not a PDF, the next most common cause is a browser extension or a flaky network choking the upload — disable extensions / open an incognito window and retry.

Which bucket are you in?

Run through this from top to bottom; the first match is almost always your fix.

Symptom you see	Likely cause	Jump to
It is a PDF with 100+ pages	Page-count limit (most common)	Cause 1
Spinner hangs only in your normal browser	Extension or stale session	Cause 2
Slow office VPN / hotel WiFi	Network throttling the upload bytes	Cause 3
File is huge (hundreds of MB) or odd format	Size cap or unsupported type	Cause 4
Small file, brief hang during a known outage	Backend processing queue	Cause 5

Common causes

Ordered by real-world hit rate, highest first.

1. PDF exceeds the 100-page limit

This is the single most common cause and the most counter-intuitive, because page count is a separate cap from file size. As of June 2026 Claude (Opus 4.7 and Sonnet 4.6) does full visual analysis — text plus charts, tables, and images — only on PDFs under 100 pages. Past that, uploads frequently stall on “Processing” or fail outright. On the API the matching error string is A maximum of 100 PDF pages may be provided.; in the web app it usually surfaces as an endless spinner or a generic upload error.

How to judge: open the PDF locally and read its page count (Preview, Adobe Reader, or your browser’s PDF viewer all show it). 100 or more pages is your problem, regardless of how small the file is.

2. A browser extension or stale session is breaking the upload

Privacy extensions, ad blockers, download managers, and even the “Claude in Chrome” extension can hook the upload POST and mangle the multipart form data. The upload looks like it started but never completes server-side. A corrupted or expired session in your normal browser does the same thing.

How to judge: retry in an incognito/private window with extensions disabled. If it works there, an extension or your cached session is the cause.

3. Network is throttling the upload

A slow or unstable connection (corporate VPN, throttled hotel WiFi, captive portal) means the upload bytes never finish reaching Claude’s servers. The UI shows “Processing” while the file is actually still in transit.

How to judge: open DevTools Network, find the upload POST, and check status. “Pending” with growing time means it is still uploading; “Cancelled” or “Failed” means it stopped.

4. File exceeds the size cap or uses an unsupported format

As of June 2026 the chat per-file cap is 500 MB, with up to 20 files per chat. (The 30 MB cap that older guides cite still applies to files added to a Project, not chat uploads.) Images can be up to 8000x8000 pixels. Supported document types are PDF, DOCX, CSV, TXT, HTML, ODT, RTF, EPUB, JSON, and XLSX (XLSX needs code execution enabled). Supported image types are JPEG, PNG, GIF, and WebP. A .pdf that is really an HTML print-to-PDF, or an obscure image format, can hang MIME detection.

How to judge: check the file size in your OS (right-click then Properties / Get Info) and confirm the real format. Then try a small, known-good file of the same type as a control.

5. Backend processing queue or an active incident

Large PDFs run text extraction and OCR before they are usable, so even a clean upload can take a minute. During an incident this stretches to several minutes.

How to judge: wait up to a minute for small files. Then check the status page — note the domain moved from status.anthropic.com to status.claude.com in 2026 — for any open file-upload or “Visual PDFs” incident.

Before you start

For PDFs, check the page count and file size locally before uploading.
Confirm the file opens correctly in your local viewer — a corrupt file will not upload.
Have a known-good small file handy for control tests.
If you are on a corporate network, note any VPN or proxy in play.

Information to collect

For PDFs: exact page count, then file size (MB) and format.
Browser + OS + network type (home / office VPN / hotel WiFi).
DevTools Network status for the upload request (pending / failed / 200).
Whether other files of similar size and format upload fine in the same session.
Timestamp of the attempt (to cross-check the status page).

Step-by-step fix

Step 1: For a PDF, check page count and split under 100

This clears the most common case first. If the PDF has 100 or more pages, extract just the pages you need:

# macOS / Linux with pdftk
pdftk input.pdf cat 1-90 output part1.pdf
pdftk input.pdf cat 91-180 output part2.pdf

# Or in Preview.app on macOS:
# File -> Print -> PDF dropdown -> save selected page range as a new PDF

Keep each part under 100 pages and upload them separately — Claude reasons across multiple attachments in one chat (up to 20 files). For a text-heavy document, copying the relevant section straight into the message box skips the file pipeline entirely; the only limit then is the context window.

Step 2: Try a known-good small file as a control

Upload a one-page PDF or a small PNG you trust. If that works in seconds, your account, browser, and network are fine and the issue is the specific file. If even the small file hangs, the issue is broader (browser, network, or Anthropic side) — go to Step 3.

Step 3: Retry in incognito with extensions off

Open an incognito/private window or a different browser, log in, and retry. If it works, the cause is a browser extension (including the “Claude in Chrome” extension), a stale session, or cache in your normal browser. Disable extensions one at a time, or clear site data for claude.ai, to find the culprit.

Step 4: Check DevTools for the real upload status

Press F12, open the Network tab, and upload again. Watch the POST request:

Status	Meaning	Fix
200	Upload reached the server	Processing/queue is the bottleneck — wait up to a minute
4xx	Server rejected it (size, type, page count, auth)	Read the response body; `A maximum of 100 PDF pages may be provided.` means split the PDF
Pending forever	Bytes still in transit	Network or VPN is slow — switch connection and retry
Failed / Cancelled	Connection dropped	Change network, disable VPN

Step 5: Re-export to a clean format

If a PDF was made by an unusual tool (browser print-to-PDF, certain scanners), re-export it:

Open in Preview / Adobe Reader -> File -> Export As PDF

For images, open in any viewer and “Save As” PNG or JPEG. This strips broken metadata and forces a clean MIME type.

Step 6: Cancel and resubmit

If processing has hung for several minutes despite a clean file:

Click the X on the thumbnail to cancel
Refresh the page
Re-upload

The processing job sometimes dies silently while the UI keeps spinning. A refresh and retry clears it.

Step 7: Check the status page

If a known-good small file also hangs in incognito, the problem may be Anthropic’s side. Check status.claude.com for an open file-upload or “Visual PDFs” incident, and wait it out.

How to confirm it is fixed

The same file (or its under-100-page split) uploads and the thumbnail switches from “Processing” to ready within about 30 seconds.
DevTools Network shows the upload returning 200.
Send a test message referencing the file (“summarize this”) and confirm Claude responds about its contents.
For PDFs, ask Claude to quote a specific line or read a value from a table — this proves it actually parsed the document, not just accepted the upload.

Long-term prevention

Pre-flight PDFs for page count, not just size — the 100-page wall causes more stuck uploads than the size cap does.
For big documents, split into sub-100-page chunks proactively, or paste the relevant text instead.
Use known-good export paths (Word -> PDF, Preview -> PDF) rather than obscure converters.
Keep one small known-good test file bookmarked for diagnostics.
For teams that upload regularly, document the current caps (500 MB per chat file, 100-page PDF visual limit, 20 files per chat) in your internal wiki and revisit them, since vendor limits change.
Re-export scanned PDFs through a clean OCR pass (Adobe Acrobat, ABBYY) before uploading — Claude’s OCR is good, but a clean preprocessed file parses faster.

Common pitfalls

Checking file size but never page count, then re-uploading the same 200-page PDF and watching it stall again.
Waiting 30 minutes hoping the queue clears, instead of splitting the PDF or retrying in incognito.
Forgetting that the 30 MB figure from old guides is the Project cap, not the 500 MB chat cap.
Blaming Claude when the real issue is a corporate VPN throttling the POST or an extension breaking it.
Re-trying the exact same file 10 times instead of running a small known-good file as a control.

FAQ

What is the actual file size limit? As of June 2026, 500 MB per file for chat uploads, with up to 20 files per chat. The 30 MB limit applies to files added to a Project, not chat uploads. Images can be up to 8000x8000 pixels.
Why does my small PDF still get stuck? Almost always page count. Claude does full visual analysis only on PDFs under 100 pages; a small but long PDF stalls or returns A maximum of 100 PDF pages may be provided. Split it under 100 pages.
Which file types can I upload? Documents: PDF, DOCX, CSV, TXT, HTML, ODT, RTF, EPUB, JSON, and XLSX (XLSX needs code execution on). Images: JPEG, PNG, GIF, WebP.
How long should processing take? A few seconds for images, up to about a minute for a normal PDF. If it is longer than that and a small control file is fine, the specific file is the problem.
Does Claude OCR scanned PDFs? Yes, but quality depends on the scan, and the 100-page visual limit still applies. Clean text PDFs are always faster.
Where do uploaded files live? They are attached to the conversation. Deleting the chat removes access to the file.

Tags: #Claude #Troubleshooting #uploads