I maintain a library that reads and writes Microsoft Excel files. Due to some recent changes neither Preview, Quicklook or Numbers can open the file. Is there are any way to get debug information from any of these (or the underlying libraries)?

I'm specifically looking for command like flags such as -d 4 which will provide more information as to why the Preview / Quicklook / Numbers can't open the file. ie. some kind of informative error message such as "can't parse the XML".

Feedback from the OOXML Working Group about relative references:

What do you mean by a relative reference? In RFC 3986, a relative reference is either an absolute-path reference (e.g., /foo/bar) or a relative-path reference (e.g., foo/bar). OPC already allows both.

So this is a bug in the Apple software stack. I'll update the bug report accordingly.

  • 1
    You really need to provide more details. What type of library do you maintain? What type of changes occurred recently? What versions of macOS and Numbers are we talking about? Anything else that may be relevant?
    – Monomeeth
    Commented Sep 28, 2016 at 13:08
  • Please attach one of your files to a new bug on bugreport.apple.com and an helpful Apple engineer will look at your file and either tell you what's wrong with it or fix it :-) Commented Sep 28, 2016 at 13:35
  • And send us the radar number here (or at least attach the file) Commented Sep 28, 2016 at 13:39
  • @ThomasDeniau "an (sic) helpful Apple engineer will look at your file...", that's very funny! Perhaps OP doesn't have a few years for someone at Apple to look at his bug report, how else can he get the debug info he's looking for?
    – fsb
    Commented Sep 28, 2016 at 14:15
  • 2
    I can't answer the question because it has been marked as unclear, but I've posted an explanation of your issue on the openpyxl bug you've posted above. You're using an absolute path for some of the relationships in your Excel file and this is invalid according to the spec. Make the paths relative like Excel does and it works with Quick Look, Preview and Numbers. See, sometimes there are helpful Apple engineers.... Commented Sep 29, 2016 at 12:51

1 Answer 1


The general manner to get at logs on macOS (and OS X in the past) is to open the Console app. It shows the common application and system logging framework and allows you to search across all sources and databases that store logs.

If you are unix based - much of this logging is documented in manual pages and at developer.apple.com.

Many third party packages have documentation - like python to interact with and document logging.

Your specific needs will depend on the exact version and build of the OS and the preview app, but start with Console and consider asking a follow on question once you have specifics.

Quicklook is going to be a much harder nut to crack, since you need to know about spotlight importer details, less direct databases and layers of indirection and storage. Spotlight debugging is more of a book than an answer here as a side question.

I'd also skip excel - since that's not really an Apple product - focus on getting your file to work in Preview and you'll likely be good to go.

  • I've got no problem reading the console logs. It's just that relevant messages aren't helpful. This is why I was looking for debug options. Commented Sep 30, 2016 at 8:33

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