I've been working on implementing a new company standard for our file naming convention (super fun), and it has been mentioned to me that there is a "standard" that says that you shouldn't use spaces in file and folder names when saving documents.

I've done some looking and I haven't found a published standard that says one way or the other whether this is acceptable. Does anyone know of a standard relating to this?


"Released Drawings" as opposed to "ReleasedDrawings" as a folder name


"123 - Rev 0 - Important part" as opposed to "123-Rev0-Importantpart"

I'm hoping to find a a specific standard, not just a rule of thumb, or best practice.

  • 1
    $\begingroup$ What operating systems are you targeting? $\endgroup$
    – Eric S
    Sep 20, 2017 at 14:14
  • $\begingroup$ Windows 10 OS, primarily CAD files, pdfs of drawings and word/excel files is what I'm working on as well if that matters any. $\endgroup$
    – Diesel
    Sep 20, 2017 at 14:16
  • $\begingroup$ You should edit your question with this necessary info. $\endgroup$
    – Eric S
    Sep 20, 2017 at 14:17
  • $\begingroup$ I had to do this for many files with a colleague and as it was only 8 and 3 back then (windows couldn't handle more than that then) we had 2 characters for the market, 2 for the model and 4 for the component number... worked well $\endgroup$
    – Solar Mike
    Sep 20, 2017 at 14:38
  • $\begingroup$ Maybe you should consider the standards used for passwords : no special characters etc... $\endgroup$
    – Solar Mike
    Sep 20, 2017 at 15:00

2 Answers 2


If you are likely to share your files with other organizations that use different operating systems, you need to research what works best on all the main options - i.e. Windows, MacOS, and the various flavors of Unix. The "If it works on Windows 10, that's OK because it's the only system we use" is probably digging a hole to fall into in future!

Spaces in file names generally cause pointless aggravation, when a system takes only the first "word" of the name as the complete name, and first complains that the file doesn't exist, and then complains that it can't understand what follows it. You can work round that by putting the whole name in quotes, but why make people do that? If you don't like ReleasedDrawings, use Released-Drawings or Released_Drawings instead.

There are other invalid characters - the most obvious being / which is the separator between parts of the file name (e.g. folders and directories) and the equivalent \ on Windows. Others are quote marks, ">", "<", "?", "*", etc. These characters have special meanings on command-line instructions in most operating systems.

Some operating systems have case sensitive file names (ReleasedDrawings and Releaseddrawings are different files!) but others do not. Windows is a compromise.

Some systems have "reserved" file names - for example COM and NUL on Windows.

There may be a limit to the total length of a file name (including all the folder names that precede it).

A Microsoft reference (obviously Windows-specific) is https://support.office.com/en-us/article/Invalid-file-names-and-file-types-in-OneDrive-OneDrive-for-Business-and-SharePoint-64883a5d-228e-48f5-b3d2-eb39e07630fa

You could do worse than stick with the POSIX specification for "fully portable filenames" which permits only characters A-Z, a-z, 0-9, "_", "-", and "." ("-" must not be the first character of the name) and a maximum length of 14 characters, or ISO 9660 (used on CDs and similar devices) which is case-insensitive and only allows A-Z, 0-9, "_", and "." with a maximum length of about 180 characters.

  • $\begingroup$ Gotcha, so while there may no be a specific standard for not including spaces, it's generally preferred more from a programming point of view. Easier file organization and better cross compatibility between OS's. The format i'm leaning towards is closer to ISO 9660, I'm a sucker for long and descriptive file names much to some peoples dismay. $\endgroup$
    – Diesel
    Sep 25, 2017 at 11:20

AFAIK, the main reason for the space convention was for url and network oriented systems, as some systems had problems when encoding/decoding spaces as parts of urls (they also look messy in a browser etc).

Various organization have their own standards such as this organization's standard


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