Here are the steps I followed to download, install, and run EpubCheck 3.0.1 on my epub.

 

1. To download EpubCheck 3.0.1, navigate to https://github.com/IDPF/epubcheck/releases using Safari and click on epubcheck-3.0.1.zip button.

 

2. Click Show downloads in Safari.

 

3. Right-click on epubcheck-3.0.1 and select Show in Finder. The finder window will show the downloaded and unzipped directory, usually /Users/myname/Downloads/epubcheck-3.0.1.

 

4. Open the Terminal application. Type the following command to change directory:

cd /Users/username/Downloads/epubcheck-3.0.1

 

5. Type:

java -version

If you get a pop up with the message:

To open “java,” you need a Java SE 6 runtime. Would you like to install one now?

 

Click Install button.

When it’s done installing, click OK on the Installing one item window.

 

6. Now ‘java -version’ should output something like this:

 

java version “1.6.0_65”

Java(TM) SE Runtime Environment (build 1.6.0_65-b14-462-11M4609)

Java HotSpot(TM) 64-Bit Server VM (build 20.65-b04-462, mixed mode)

 

7. Now run:

java -jar epubcheck-3.0.1.jar /Users/username/Documents/mybook.epub > mybook.epub.errors 2>&1

 

8. A file called mybook.epub.errors will have been created in your current directory (/Users/myname/Downloads/epubcheck-3.0.1).

 

9. You can view the file by running:

less mybook.epub.errors

Press ‘q’ to exit.

10. Alternatively, you may right-click the file in a Finder window and select Open with→Other. Select TextEdit from the Applications directory. You will see a window with the contents of mybook.epub.errors.