Editing Filename (section)

{{short description|Text string used to uniquely identify a computer file}}
{{Use mdy dates|date=October 2017}}
[[File:Dir command in Windows Command Prompt.png|thumb|Screenshot of a [[Microsoft Windows|Windows]] command shell showing filenames in a directory]]
[[File:EMule v.049b.JPG|thumb|Filename list, with long filenames containing comma and space characters as they appear in a software display.]]

A '''filename''' or '''file name''' is a name used to uniquely identify a [[computer file]] in a [[file system]]. Different file systems impose different restrictions on filename lengths.

A filename may (depending on the file system) include:
* '''name''' &ndash; base name of the file
* '''[[Filename extension|extension]]''' – may indicate the [[File format|format of the file]] (e.g. <code>.txt</code> for [[plain text]], <code>.pdf</code> for [[Portable Document Format]], <code>[[.dat]]</code> for unspecified binary data, etc.)

The components required to identify a file by utilities and applications varies across operating systems, as does the syntax and format for a valid filename.

The characters allowed in filenames depend on the file system.  The letters A–Z and digits 0–9 are allowed by most file systems; many file systems support additional characters, such as the letters a–z, special characters, and other printable characters such as accented letters, symbols in non-Roman alphabets, and symbols in non-alphabetic scripts. Some file systems allow even unprintable characters, including [[Bell character|Bell]], [[Null character|Null]], [[Carriage Return|Return]] and [[Linefeed]], to be part of a filename,<ref>{{cite web
 |title=Fixing Unix/Linux/POSIX Filenames: Control Characters (such as Newline), Leading Dashes, and Other Problems
 |url=https://dwheeler.com/essays/fixing-unix-linux-filenames.html
 |author=David A. Wheeler
 |date=2023-08-22<!--  (originally 2009-03-24) -->
 |access-date=2024-07-14
 |url-status=live
 |archive-url=https://web.archive.org/web/20240525183611/https://dwheeler.com/essays/fixing-unix-linux-filenames.html
 |archive-date=2024-05-25
}}</ref> although most utilities do not handle them well.

Filenames may include things like a revision or generation number of the file,
a numerical sequence number (widely used by [[digital camera]]s through the [[Design rule for Camera File system|''DCF'' standard]]),
a date and time (widely used by [[smartphone camera]] software and for [[screenshot]]s),
or a comment such as the name of a subject or a location or any other text to help identify the file.

Some people use the term filename when referring to a complete specification of device, subdirectories and filename such as the Windows ''C:\Program Files\Microsoft Games\Chess\Chess.exe''.
The filename in this case is ''Chess.exe''.
Some utilities have settings to suppress the extension as with MS Windows Explorer.{{Not verified in body|date=July 2023}}