ChatGPT Unknown Error When Uploading PDF? Here’s How to Fix It

Getting a ChatGPT unknown error when uploading a PDF? You’re not alone. Many users face this frustrating issue when trying to upload PDFs for tasks like summarization, content extraction, or report analysis. Whether you see a message like “unknown error occurred” or “error uploading PDF to ChatGPT”, it’s often caused by file size limits, unsupported formatting, or temporary platform glitches.

In this guide, we’ll walk you through the most common reasons behind the ChatGPT PDF upload error and show you how to fix it step by step.

If you're exploring ChatGPT's latest features, check out ChatGPT-4o: A Leap Forward in AI Technology for a deep dive into its new capabilities or learn how OpenAI’s latest release changes everyday workflows in ChatGPT’s New Voice and Image Update.

Common Causes of the “Unknown Error” When Uploading PDFs to ChatGPT

1. File Size Limitations

ChatGPT has a file size limit for uploads. If your PDF exceeds this limit, the platform may reject the upload with an unknown error. While OpenAI hasn’t explicitly published a maximum file size, users have reported that files over 20-25 MB often fail to upload.

Solution:

• Compress your PDF using online tools like Smallpdf or Adobe Acrobat’s compressor.

• Split large PDFs into smaller sections and upload them separately.

2. Corrupted or Improperly Formatted PDFs

If your PDF file is corrupted or contains formatting errors, ChatGPT may be unable to process it properly. This can happen due to:

• Incomplete file downloads

• Issues during PDF creation or export

• Malformed PDF metadata

Solution:

• Open the PDF in a viewer like Adobe Acrobat and try re-saving it as a new PDF file.

• Use the "Print to PDF" option in your document viewer to create a fresh, clean version of the file.

3. Browser Issues

Your browser may be causing conflicts that prevent successful uploads. This could be due to:

• An outdated browser version

• Cached files or cookies interfering with functionality

• Extensions or ad blockers that disrupt file upload processes

Solution:

• Update your browser to the latest version (Chrome, Firefox, Edge, or Safari).

• Clear your cache and cookies by going to browser settings.

• Disable browser extensions, especially ad blockers or security plugins, and try uploading again.

• Try switching to incognito mode and see if the issue persists.

4. Temporary Server Issues

Sometimes, the issue isn’t on your end—OpenAI’s servers may be experiencing temporary downtime or high traffic, causing file uploads to fail.

Solution:

• Check OpenAI’s status page for any reported outages.

• Wait for some time and try uploading again later.

• Refresh the page and attempt the upload again.

5. Unsupported PDF Content

Certain elements in your PDF may be incompatible with ChatGPT’s file processing capabilities, including:

• Encrypted or password-protected PDFs

• Embedded multimedia files (audio, video, or interactive elements)

• Non-standard fonts or complex formatting

• Scanned images without selectable text

Solution:

• Remove encryption or password protection before uploading.

• Convert scanned PDFs into searchable text using OCR (Optical Character Recognition) tools like Adobe Acrobat’s OCR or online services like i2OCR.

• Simplify the PDF by removing unnecessary elements.

6. Uploading From an Incompatible Device or Network Issues

Sometimes, the issue may be linked to your device or internet connection.

• Using an unstable internet connection can result in incomplete file uploads.

• Firewalls, VPNs, or corporate network restrictions may block file uploads.

• Some mobile browsers may not support file uploads properly.

Solution:

• Ensure you have a stable internet connection before uploading.

• Try switching to a different Wi-Fi network or disabling your VPN.

• If using a mobile device, switch to a desktop or laptop for better compatibility.

Get More From ChatGPT & AI Tools

ChatGPT is part of a larger movement shaping the future of tech. To better understand that shift, explore How Generative AI Is Changing the Digital Landscape—a breakdown of how tools like ChatGPT are being used across industries.

And if you're a content creator or marketer concerned about AI-authored content, learn how to protect your brand with Winston AI: The Best AI Content Detector—a must-have for detecting and reviewing AI-written material.

Frequently Asked Questions

Why do I get an "Unknown Error" when uploading a PDF to ChatGPT?

This error typically happens because of file size issues, corrupted files, or incompatible formatting. ChatGPT reads standard PDF documents, but if your file contains advanced encryption, excessive images, or is partially damaged, the system might not process it. Before re-uploading, try repairing the file using trusted tools like Adobe Acrobat’s Repair PDF or the free PDF24 Repair Tool, both of which are safe and widely recommended.

What is the maximum PDF file size ChatGPT accepts?

While OpenAI doesn’t officially list a maximum size, community tests show keeping your PDF under 10 MB is a good practice. Larger PDFs with high-resolution images or scans tend to fail. To reduce your file size without losing quality, use trusted services like Adobe Acrobat Online Compressor or Smallpdf PDF Compressor. These tools compress while maintaining readability.

How do I check if my PDF is corrupted before uploading?

A quick way is to open your PDF with reliable software such as Adobe Acrobat Reader. If the document shows errors, or doesn't open at all, it might be corrupted. To repair it, you can use free online solutions like iLovePDF Repair PDF or PDF24 Repair Tool, both of which scan your file and fix structural problems.

Can password-protected PDFs be uploaded to ChatGPT?

No, ChatGPT cannot process password-protected or encrypted PDFs. You will need to remove the protection first. Use secure tools such as Adobe’s Unlock PDF or Smallpdf Unlock PDF, which help unlock your file safely and maintain your data privacy.

Are scanned or image-heavy PDFs causing upload failures?

Yes, they often do. Scanned PDFs that are essentially image files tend to be larger and harder for ChatGPT to interpret. To improve the upload success rate, convert your scanned file into text using OCR (Optical Character Recognition). Recommended solutions include Adobe Acrobat Pro OCR and the free OnlineOCR.net, which accurately converts images into editable text.

What should I do if I’ve fixed the file but the error still happens?

If you’ve optimized the PDF and the error persists, the issue might be browser-related or on OpenAI's side. Try these steps:

• Clear your browser cache and cookies: Google Chrome clear cache

• Use incognito mode or switch to another browser like Firefox or Edge

• Check the current service status on OpenAI’s status page

• If the problem continues, report it directly through OpenAI Community, where engineers track issues.

Final Thoughts: "Unknown Error" When Uploading a PDF to ChatGPT

While the "Unknown Error" when uploading PDFs to ChatGPT can be annoying, it's often fixable with a few simple troubleshooting steps. By compressing your file, reformatting it, clearing your browser cache, or checking OpenAI’s server status, you can usually resolve the issue quickly.

If the problem persists, consider reaching out to OpenAI's support team for further assistance.