SingleInstance: allow only one running instance of a program


Have you ever launched a program and started working with it only to discover that there’s another instance of it running in the background? This can be a mild annoyance from time to time, especially when you realize after a few minutes that the two instances have the same file or data open and that your unsaved modifications are slightly different in each one and you are unsure which of the two (if any) was last saved to the hard drive.

I set out to find a program that might prevent this sort of thing, and I present to you: SingleInstance an Autohotkey script that runs in the background, consumes very low resources, and can prevent the duplication of running instances for specific user-defined programs.


Here are more notes on this app:

  • SingleInstance settingsHow it works: first off, you need to find out the name of the executable that you want to suppress multiple instances of. Next, simply type or paste the name (e.g. “Revouninstaller.exe”, without the quotes) in the settings. Note that SingleInstance doesn’t actually suppress the running of this program at any point, but will shut it down immediately once it detects the second instance, and switch the focus back to the first intance.
  • Enabling/disabling: of the program activity can be checked on and off from the system tray menu.
  • Hidden programs: are also detected (optional)
  • Resource consumption: a very small 4 megs in memory.
  • Portable: just run the executable. Program settings are saved in an .ini file in the same directory.
  • A note on Autohotkey scripts: some antivirus programs erroneously flag these scripts as malware (although this is becoming quite rare). If this happens in your system, do not be alarmed, it is a false positive.

The verdict: a tiny but quite useful app. It does a very simple thing but does it well, and consumes hardly any resources at all. If you want a solution to the multiple running instances problem SingleInstance provides a very good one.

Version Tested: 1.0

Compatibility: Winall

Go here to download (approx 421K). This app is featured on the famous “Skrommel’s one hour software” page.