# How can I run two instances (or equivalent) of Slic3r on OS X?

I am modifying some Slic3r config parameters and comparing the results. How can I have two instances (or equivalent: I would like to see two model windows with their associated configuration screens) of Slic3r at the same time? I'm on OS X, but if there is a generic (e.g. within Slic3r) solution that will be preferrable.

• Mark, The answer to your question is available here: stackoverflow.com/questions/47350555 – Samveen Nov 5 '18 at 5:01
• Thanks Samveen, much appreciated! I think you should consider that it might be useful here to answer questions related to running 3D printing software, such as slic3r. There could have been specific slic3r commands or configuration options that are useful for doing this. Cheers and thanks again! – Mark Harrison Nov 5 '18 at 6:18
• @Samveen If you look at Game plan - What is on-topic? I'm inclined to say that this falls in the category of "Software issues" and should not be closed. – 0scar Nov 5 '18 at 7:48
• Yes, this could go anywhere including Ask Different, SuperUser... however, we have an answer now, and everything is upvoted, so even if it is closed, then it will never be deleted :-) – Greenonline Nov 5 '18 at 8:29
• @MarkHarrison however, this is very much purely a question of how to handle executables under OS X. the fact that you are dealing with Slic3r is irrelevant. Now, if you want to ask how to make Slic3r do two different slices on one object at the same time, then this would be on-topic. – Carl Witthoft Nov 5 '18 at 18:58

You could duplicate the application by clicking on the application and pressing Command (⌘) + D, and then run both - although I'm not sure if that would mess with the preferences. I haven't fully tested it, but both instances opened up and worked, seemingly ok.

You could even rename them to something other than "Slic3r" and "Slic3r copy" to remind you which application is slicing which model, for example:

• "TestCube" and "Benchy", or;
• "Slic3r-TestCube" and "Slic3r-Benchy", or whatever.

However, Mark's answer seems much more elegant.

• So far as Preferences and whatnot go: that depends on whether Slic3r stores all config files inside its own application folder or in /usr/lib/[whatever] . However, if one follows Mark H's answer, you'll guarantee that whatever changes to config or prefs you do in either instance will change the only existing prefs. files. That makes your answer slightly safer! – Carl Witthoft Nov 5 '18 at 19:00

From a terminal window, run the command

open -n -a slic3r


Each time the command is executed, a new instance of Slic3r is created.

As per Carl's note, keep in mind that both instances of Slic3r will be sharing the same configuration files, so it will be safest not to save configuration changes while both are open.

• See comments about Prefs files under Greenonline's answer – Carl Witthoft Nov 5 '18 at 19:01