Technology Training

Technology Training & Support Resources from LPS Computing Services

File Names

Computer users frequently save files. Every time they do, they are faced with a small decision – “What should I name this file?” Some of you have never given this a second thought and have been just fine, while others have learned through difficult experiences that some file names are better than others. Because this is a question that pops up on a regular basis, please consider the following information:

Every operating system ever used to control a computer (Macintosh, Windows, etc.) has had a slightly different set of rules about what you can and cannot do when naming your files. This is typically not a problem until you intend to move files from one place to another, or share your files with people who may be using a different type of computer than you are. The following rules should keep your filenames appropriate, no matter what computer or server will see them over the years.

The following characters will always be safe:

  • Aa-Zz    (alpha characters)
  • 0-9        (numeric characters)
  • _        (underscores)
  •         (hyphens)

For various technical reasons the following characters should NOT be used in any file name:

  •  ⁄    (back slash or forward slash)
  • :     (colon)
  • *     (asterisk)
  • ?     (question mark)
  • ”     (quotation marks)
  • < > (angle brackets/less than/greater than)
  • |     (pipe)
  • %     (percent)
  • #     (number/pound/hash)
  • $     (dollar)
  • ,     (comma)
  • ;     (semi-colon)
  • •     (bullet)
  • &     (ampersand)


Your filename should end with a three letter extension identifying to computers what software is necessary to view the file. Your computer will assist you with this whenever you save a file. Use a period to separate the base file name from the file extension, but do not use two consecutive periods or one after the file extension. For example:

GOOD:     Filename.pdf

BAD:     Filename..pdf

BAD:     Filename.pdf.

Also BAD:

Avoid giving a file more than one file extension ( as it gives the impression the file is trying to hide its real identity, making it appear like a virus. Email and web filters may block this file.

File Name Length

Early file systems limited names to 8 characters in length. That increased to 32 characters in the 90’s, and then to the current standard which is 255 characters allowed in a file name. However, having the ability to give a file a really long name does not make it a good idea. Consider the act of viewing a file in a folder (on your computer, or eDisk), or on a web page (DocuShare). Files with names longer than 11 characters or so become difficult to view, and are often truncated for viewing.  For this reason, try to keep your total file names under 15 characters.

Other Tips

Within a single folder (directory) no two files may have the same name. Your computer will often make adjustments for you to avoid replacing a file. For example:

  • Filename.pdf
  • Filename01.pdf
  • Filename02.pdf
  • Filename03.pdf

File names are not case sensitive. Upper-case letters and lower-case letters are considered the same. The file names “MyName.pdf” and “myname.pdf” would be considered identical, and a folder could not contain both of them.  If you try to add a file with the same name to a folder, your computer may ask you if you wish to replace the original.  Consider carefully.


Email Attachments

All of the same rules above apply to files that you wish to send as attachments to email messages.  File extensions are especially important when sending email attachments.  They help the email programs understand what helper applications are required to open the file.


More Information

Again, every operating system has its own set of rules, and what works on one may not be acceptable on another. For more details, feel free to refer to the following resources: