28 Media Upload Validation Errors

Users of your Pressbooks network may occasionally receive errors when attempting to upload certain file types. Read on for more information on:

File Uploads & Network Security

Pressbooks is not designed to function as a file storage/publication platform. If users would like to refer to or provide links to files for demonstration or learning purposes, we generally recommend that they host these files externally — Youtube, Vimeo and campus-provided media streaming services are good choices for video and large audio files, and sites like GitHub, Google Drive, Box, or Dropbox offer good cloud hosting options that should meet most users needs to host and refer to external files in their books.

While Pressbooks allows users to upload certain types of media files to a book’s media library and embed/include them within their books, users are limited in the types of files that can be uploaded to Pressbooks. We do this because many file types can pose a potential security risk to readers and other users of the network.

As a result, you or a user on your network may receive the error: “Sorry, this file type is not permitted for security reasons.”

File type is not permitted error

This error will appear when a user attempts to upload media to their book that isn’t included in the list of permitted file types for your network.

Debugging File Type Errors

As a network manager, you can verify the reason why a file wasn’t able to upload by following these steps:

  1. Navigate to Tools > Debug File Validation from the left sidebar menu of the book dashboard
  2. Click Choose File and upload the file that caused the error
  3. Click Upload 
Debug File Validation upload screen

You will receive an Analysis report that lists out why the file wasn’t accepted. This list may include the following:

  • WordPress will not process this file based on its name
  • This file type is not allowed
Debug File Validation report

Allowing File Types

On Pressbooks, there are set number of file types which are allowed by default. If you want to upload file type that is not included in the list of defaults, you can put in a request to have additional file types/extensions permitted on your network.

The allowing of additional file types can only be done by Pressbooks staff, and any requests will be reviewed for security concerns before a decision is made. If any network managers wants to inquire about or request the allowing of a particular file type on their network, please contact our premium support desk.


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The Pressbooks Network Manager's Guide by Pressbooks is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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