FLS Checker

Recently, the limited number of ‘Fibre Link Storage’ slots available on Windows application became a serious bottleneck for any windows daw written in C++.  Each vst plugin uses a small number of the FLS slots, plugins from the same vendor shares library they use. But then once the number of the slots used in a process reached 128, it won’t be able to open any more dll files. Thus a plugin fails to initialize on the daw without any apparent reason.

Daw and plugin makers are aware of this problem and already started to update their products to use fewer slots possible, however you still see this problem in many cases. There are lots of reports related this on public forums.

I have built a simple plugin that shows the number of the FLS slots available. It will report the number when its GUI is opened, or when the update button is clicked. It uses 1 slot by itself.

VST2 & VST3 x64 Download <- Your web browser warns you that this file may be dangerous, but please don’t worry. 🙂




8 Replies to “FLS Checker

  1. Fantastic! Great to be able to at least monitor the problems so easily, knowing about the actual headroom, thanks a thousand times!

  2. Hi All

    The latest Windows 10 Insider preview (18312) increases the available per-process FLS slots from the Vista-era 128 to a bit over 4000. Note that the FLS Checker plugin maxes out at 128, so even after adding a ton of hungry plugins to my DAW, it still shows 128.

    If all goes well with testing, this will be in the 19h1 Windows 10 release in the first half of this year.

  3. takashi, thanks for this plugin !
    Windows released 1903 today (05-22-2019) so can you make an updated version of the plugin?
    TIA !

  4. This is a god-send, Takashi. Thank you so very much.
    I’ve been chasing my tail on a huge project where I was unable to load otherwise extremely reliable plugins.
    Turned out zero FLS slots were available.

    All the best from London!
    Dax Liniere.

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