What are (un-)allowed characters for folders and files

I am astonished that I could not find any post oder documentation page about what characters are (not) causing problems with what-ever NC function.

Out of the NC world some it freaks propose to use the ASCII characters but for NC “/” and " / " do cause problems whereas spaces, German Ä, Ü and Ösaren’t…

Or to ask differently: What characters do we have to avoid else than:

< > ? " : | \ / *.’

Hi Mut-Tour

There is something called “reserved characters” which applies to each file system on each operating system. This is nothing NC could change or be held responsible for. This is probably why you couldn’t find anything in any documentation.

The following characters should never be used as folder or file names (on Windows you could not use these anyway, as Windows would tell you, that these characters are not allowed):

The following reserved characters:

  1. < (less than)
  2. > (greater than)
  3. : (colon)
  4. " (double quote)
  5. / (forward slash)
  6. \ (backslash)
  7. | (vertical bar or pipe)
  8. ? (question mark)
  9. * (asterisk)

The German Umlauts (Ü, Ö, Ä, ü, ö, ä) shouldn’t cause any problems, since these are no reserved characters for any file system typical action.

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For collabora, the % character should be avoided - it crashes on opening files where the name contains % .



I confirm problem with % character in filename in nextcloud 14.0.3 not only cause of collabora.

I get this problem and search a way on how to solve it.

Is it a way to restrict character in filename when they are upload or sync?


using a more recent Collabora , filenames containing % are working perfectly:


4.0.6 (git hash: dbfdf5d4)


Collabora OfficeDev 6.0-31 (git hash: 9e571fc)

The # is also a character which give problems. I can’t open a file with a # in the filename