Answers.Body: <p>That would mean your EPUB does not have a proper ZIP file structure. </p>
  
  <p>You can try listing the content of your file with a normal zip unpacker, or test it with a real epubreader. If those do not complain, it could mean that FlightCrew has a bug.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-01-17T14:55:49.380Z
Answers.Text: You are right, I used 7zip after FlightCrew complained about mimetype not being the first file within the `.epub`. This resulted in generating a `.7z` file, which is indeed no valid `.zip`.
Answers.UserDisplayName: Tim
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-01-17T14:34:20.657Z
Answers.LastActivityDate: 2014-01-17T14:34:20.657Z
Answers.UserDisplayName: Anthon
Body: <p>I am experimenting with building my own <code>.epub</code> files and try to validate them using <a href="http://code.google.com/p/flightcrew/" rel="noreferrer">FlightCrew</a>.</p>
  
  <p>Currently it says my file is invalid because it is</p>
  
  <blockquote>
    <p>Unable to find zip structure: End-of-central-directory</p>
  </blockquote>
  
  <p>What could this mean what could be the reason for such a message?</p>
  
Tags: <epub><validation>
Title: What does FlightCrew's "Unable to find zip structure: End-of-central-directory" mean?
UserDisplayName: Tim
ThreadText: # What does FlightCrew's "Unable to find zip structure: End-of-central-directory" mean?
  
  (Asked by: username_0 on 2014-01-17)
  
  I am experimenting with building my own `.epub` files and try to validate them using [FlightCrew](http://code.google.com/p/flightcrew/).
  
  Currently it says my file is invalid because it is
  
  > Unable to find zip structure: End-of-central-directory
  
  What could this mean what could be the reason for such a message?
  
  **Tags:** epub, validation
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2014-01-17. Score: 8 | Accepted answer
  
  That would mean your EPUB does not have a proper ZIP file structure.
  
  You can try listing the content of your file with a normal zip unpacker, or test it with a real epubreader. If those do not complain, it could mean that FlightCrew has a bug.
  
  > **Comments:**
  > **username_0**: You are right, I used 7zip after FlightCrew complained about mimetype not being the first file within the `.epub`. This resulted in generating a `.7z` file, which is indeed no valid `.zip`.  
  
  ---
  
  