On my iMac this works perfectly. I have application open, I open a file extension handled by that application and it will open in the already open application. Just got a new Macbook Pro and each time I open a file it will open the same application again.


I open an HTML file in Sublime Text 2, instead of using the application that is already open like on my iMac, it opens in it's own Sublime Text 2. Doesn't matter how many files I open. Each time it will open a new application.

Click a link from an email? New Chrome window will launch. I have Chrome open already, but it will open a new window every time. Double click an HTML file on the desktop? New Chrome window.

Very annoying so what is the setting I need to check that will stop this behavior and always open in the already open instance of the application?

  • What version of OS X is installed on each, the same or different? – user3439894 Jul 15 '15 at 0:55
  • Sorry, yes the are both Yosemite and both up to date with all current updates. – o_O Jul 15 '15 at 1:26
  • The new MBP is fresh out of the box. I've installed applications on it but not messed with the settings any. – o_O Jul 15 '15 at 1:26
  • It's likely that you are using the world instance to mean window, as it has been pointed out. There's no system-wide setting to instruct apps to using new windows, as far as I know. – fartheraway Jul 15 '15 at 3:25

If you are saying that you want each double-click to open the new file in a new tab of the current Sublime window, rather than opening a new window in Sublime, then that is going to be an application-specific preference. Meaning, you'll need to look at the preferences for Sublime and see if there isn't some equivalent of "Open new file in tab" or "Open new window in new tab" setting.

  • I can't remember exactly what I did to fix it but I think it was in the preferences. – o_O Jul 22 '15 at 19:22

I wonder if you need to set file associations for some file types on the new MBP? some of the defaults are probably different than on you trusty iMac. You can check each file by hitting command-I in Finder with the file highlighted. Here is an explanation: http://osxdaily.com/2013/08/08/change-default-application-open-files-mac-os-x/ Each file type has a default application that is associated with it. This means that when you double-click a file from the Finder it will open a specific application, for example on a fresh Mac OS X installation, all image files (png, jpg, gif, pdf, etc) will default to opening in Preview, and all text documents (txt, rtf, etc) will open in TextEdit. Over time, the default applications and file associations can change as you install more applications, which sometimes set themselves as the new default app to open a file format with.

  • That's well and good but would that default control whether it opens a new instance each time or not? For example, I can set all HTML documents to open in Sublime. If I then double click it will open in Sublime. If I double click another HTML file, does it now open in a new instance or the same open Sublime? I don't know if you were reading my question to be about defaults or if you're saying the defaults could be interfering with the way they're opening applications. – o_O Jul 15 '15 at 2:03
  • Just set all HTML docs to open with sublime by default. Double click first file, opens Sublime. Double click second file, opens a second instance of Sublime. Doesn't look like that works. – o_O Jul 15 '15 at 2:06
  • @RKS, Are you sure it's another instance, in other words there is more then one occurrence of Sublime Text 2 in Activity Monitor, or is it just a second window of the original instance of Sublime Text 2? Which BTW are two different things. BTW I just tested opening documents in Sublime Text 2 and the second file opened in a second window of the only running occurrence. So this appears to be normal. – user3439894 Jul 15 '15 at 2:09
  • Normally on my iMac it behaves as you describe. Each new file opened is a new tab in one sublime. For me, each one opens in a separate window. I will need to check if they are two lines in the activity monitor like you said. In the meantime, do you know what the fixes are for each version of your question? – o_O Jul 15 '15 at 3:06

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