ChatGPT “Unknown Error Occurred” on File Upload

If you’ve been trying to upload a PDF, DOCX, or other files to ChatGPT and keep seeing the dreaded message:

“Unknown error occurred”

…you’re not alone. Many users have recently reported issues with file uploads in ChatGPT 4o and other versions, especially when trying to share lecture slides, notes, or large PDFs. What’s even more frustrating is that it may have worked perfectly fine a few days ago, only to suddenly stop working without explanation.

So, why does this happen, and how do you fix it? Let’s break it down.

Common Causes of the Error

Temporary outages or server-side issues
- Sometimes the issue isn’t on your end at all. OpenAI servers or the file-processing API may be experiencing downtime.
Unreadable PDFs (scanned or image-based)
- If your file is a scanned document (essentially just images), ChatGPT cannot extract text from it unless it has been processed with OCR (Optical Character Recognition).
Corrupted or incompatible file formats
- Even if it’s a valid PDF, it may contain embedded objects, unusual formatting, or compression that prevents ChatGPT from reading it.
Account-specific glitches
- Some users have reported that uploads fail on one account but work on another. This could indicate a temporary flag or restriction on the account.
Browser or app cache issues
- Old cache and cookies can sometimes interfere with the file upload process.

How to fix ChatGPT “Unknown Error Occurred” on File Upload : iPhone/PC/Android

Here are solutions tested by other users:

✅ 1. Convert the PDF with OCR

If your PDF is scanned or image-based, run it through an OCR tool first. Options include:

Adobe Acrobat OCR (paid but very reliable)
iLovePDF OCR (free online option)
SmallPDF OCR or similar tools

Once converted to searchable text, re-upload the file to ChatGPT.

✅ 2. Try a Different Browser or Device

Use Chrome, Safari, or Edge instead of your usual browser.
If you’re on desktop, try uploading the file from your mobile app (iPhone, iPad, or Android).

Some users report the error only appears on desktop browsers but works fine on mobile.

✅ 3. Re-Save or Compress the File

Open the PDF in any editor (like Preview on Mac or Word on Windows).
Choose Save As → PDF (reduced size).
This can strip out hidden formatting or corruption that ChatGPT struggles with.

✅ 4. Clear Browser Cache or Use Incognito Mode

Clear cache and cookies for chat.openai.com.
Or open a new incognito/private browsing window and try again.

✅ 5. Test With Another Account

Some users discovered file uploads worked perfectly fine when logged into a different OpenAI account. If you have access to another account, test it there.

When Nothing Works

If none of the above solutions help, it’s very likely a temporary outage or bug on OpenAI’s end. In that case:

Report the issue via Settings → Help → Report a Problem.
Monitor OpenAI’s status page for updates.
As a workaround, extract the text from your PDF using an OCR tool, then paste it into ChatGPT manually or split it into smaller chunks.

Final Thoughts

The “Unknown error occurred” file upload bug in ChatGPT is frustrating but usually fixable. The most common culprit is PDFs without readable text, which can be solved by converting them with OCR. If the issue persists across multiple files and devices, it’s likely a temporary glitch that OpenAI needs to fix.

Until then, converting your documents and trying alternate browsers, devices, or accounts should help you keep working on your study notes without interruptions.

👉 Pro tip: If you’re using iPhone, iPad, or Android, the ChatGPT app often handles uploads more smoothly than desktop browsers.