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Ask HN: Are there legal limits for filename extensions for proprietary software?

I wanted to create a file format for describing nests of files for ease of access with my application. I discovered the extension I thought of to go with my naming scheme was in use by a megacorporation for one of their many pieces of software. What liability would I face for using this file extension, and would it be better to adjust it than attempt to solve any future conflicts?
( 5 comments | 3 points | on HN )
Re:Ask HN: Are there legal limits for filename extensions fo... by theGeatZhopa on Wednesday February 23, 2022 @01:39AM (#30438377)
Worry a lot :) your extension might just wrongly open with an wrong Software because it's associated/linked just to that program. Like .doc is linked to Word.

So it's better to choose w unique extension. Since we're out of 8.3 era - nothing holds you from the 8.4 or xxx.5 scheme. The only thing is to keep an eye onto what filesystems can take. NTFS is suitable for 256 characters, but I'm not sure if the dot and extension is within this maximum or not.

Re:Ask HN: Are there legal limits for filename extensions fo... by warrenm on Wednesday February 23, 2022 @01:31PM (#30444535)
I have a tool (MindNode) that thinks ".md" is supposed to belong to it

Which is stupid

Because markdown has been using ".md" for far longer than MindNode's been around

But c'est la vie - I just make sure I have ".md" associated with my markdown editor of choice, and force MindNode to only open files through File->Open

Re:Ask HN: Are there legal limits for filename extensions fo... by weichsel on Friday February 25, 2022 @06:48AM (#30466264)
Hi, I am one of the engineers working on MindNode. We don’t register MindNode as the owner of “md”, but as an app that can open and save to this file type. If we don’t do this we are unable to import and export Markdown files. You can change the default app anytime in Finder by using “Get Info (cmd+i)” and choose an app in the “Open with:” section of the Info window. If you need further assistance, please contact us via "Send us an Email" on https://www.mindnode.com/support
Re:Ask HN: Are there legal limits for filename extensions fo... by wmf on Wednesday February 23, 2022 @01:11AM (#30438217)
Don't worry about it; every extension is already used by multiple apps.
Re:Ask HN: Are there legal limits for filename extensions fo... by brudgers on Wednesday February 23, 2022 @02:00PM (#30444862)
Make a choice one way or the other and move on. You've already spent too much energy on it. Good luck.