Desktop Entry Standard

Version 0.9.2

Table of Contents
1. Introduction
2. Basic format of the file
3. Possible value types
4. Recognized desktop entry keys
5. Character set encoding of the file
6. List of valid Exec parameter variables
7. Detailed discussion of supporting MIME types
8. Extending the format
A. Example Desktop Entry File
B. The Legacy-Mixed encoding

1. Introduction

Both the KDE and GNOME desktop environments have adopted a similar format for "desktop entries," or configuration files describing how a particular program is to be launched, how it appears in menus, etc. It is to the larger community's benefit that a unified standard be agreed upon by all parties such that interoperation between the two environments, and indeed any additional environments that implement the specification, becomes simpler.


2. Basic format of the file

These desktop entry files should have an extension of ".desktop" or ".kdelnk". ".kdelnk" is deprecated, and is only maintained for backwards compatibility. Determining file type on basis of extension makes determining the file type very easy and quick. When no file extension is present, the desktop system should fall back to recognition via "magic detection." Desktop entries which describe how a directory is to be formatted/displayed should be simply called ".directory".

The basic format of the desktop entry file requires that there be a "group" header named "[Desktop Entry]". For backwards compatibility, implementations may also support the header "[KDE Desktop Entry]". This "group" entry denotes that all {key,value} pairs following it belong in the Desktop Entry group. There may be other groups present in the file (see MIME types discussion below), but this is the most important group which explicitly needs to be supported. This group should also be used as the "magic key" for automatic mime type detection. There should be nothing proceeding this group in the desktop entry file but possibly one or more comments (see below).

Lines beginning with a "#" are considered comments and will be ignored, however they should be preserved across reads / writes of the desktop entry file.

Compliant implementations MUST not remove any fields from the file, even if they don't support them. Such fields must be maintained in a list somewhere, and if the file is "rewritten," they will be included. This ensures that any desktop-specific extensions will be preserved even if another system accesses and changes the file.

Entries in the file are {key,value} pairs in the format:

Name=Value

Space before and after the equals sign should be supported; the "=" sign is the actual delimiter.


3. Possible value types

The value types recognized are string, localestring, regular expression, boolean (encoded as the string true/false), and numeric.

The difference between string and localestring is that the value for a string key must contain only ASCII characters and while the value of a localestring key may contain localized encodings. (See section 5.)

Some keys can have multiple values; these should be separated by a semicolon. Those keys which have several values should have a semicolon as the trailing character.


4. Recognized desktop entry keys

Keys may be postfixed by [locale], where locale is the LOCALE type of the entry. locale must be of the form lang[_COUNTRY][.ENCODING], where either _COUNTRY or .ENCODING may be omitted. If a postfixed key occurs, the same key must be also present without the postfix.

When reading in the desktop entry file, the value of the key is selected by matching the current POSIX locale for the LC_MESSAGES category against the locale postfixes of all occurrences of the key, with the .ENCODING part stripped. (The .ENCODING is used when the Encoding key for the desktop entry file is Legacy-Mixed, see Appendix B.)

The matching is done as follows: if the current value of LC_MESSAGES is lang_country.encoding@modifier, then, if a key for lang_country is present, it will be used. Otherwise, if a key for lang is present, it will be used. If both of these are missing, the required key without a locale specified is used. The encoding and modifier from the LC_MESSAGES value are ignored.

For example, if the current value of the LC_MESSAGES category is de_DE, and the desktop file includes:

 Name=Foo
 Name[de]=Foo auf Deutsch

Then the value used for the name key will be 'Foo auf Deutsch'. However, if a value is specified for Name[de_DE], then that will be used instead.

Case is significant. The keys "Name" and "NAME" are not equivalent. The same holds for group names. Key values are case sensitive as well.

Keys are either OPTIONAL or REQUIRED. If a key is optional it may or may not be present in the file. However, if it isn't, the implementation of the standard should not blow up, it must provide some sane defaults. Additionally, keys either MUST or MAY be supported by a particular implementation.

Some keys only make sense in the context when another particular key is also present.

Some example keys: Name[C], Comment[it].

Table 1. Standard Keys

KeyDescriptionValue TypeREQ?MUST?
Encoding encoding of the desktop entry file stringYESYES
Version version of Desktop Entry Specification numeric (4)NOYES
Name name of the entry, need not match binary name localestringYESYES
Type the type of desktop entry string (1)YESYES
FilePattern a list of regular expressions to match against for a file manager to determine if this entry's icon should be displayed. Usually simply the name of the main executable and friends. regexp(s)NONO
TryExec filename of a binary on disk used to determine if the program is actually installed. If not, entry may not show in menus, etc. stringNONO
NoDisplay whether not to display in menus, etc. booleanNONO
Comment descriptive comment localestringNOYES
Exec program to execute, possibly with arguments stringNOYES
Actions additional actions possible, see MIME type discussion in Section 7 string(s)NOYES
Icon icon to display in file manager, menus, etc. the icon MAY specify a specific path to override common search directories stringNOYES
MiniIcon small icon for menus, etc (deprecated). stringNONO
Hidden if true, pretend this entry doesn't exist. booleanNONO
Path if entry is type Application, the working directory to run the program in. stringNOYES
Terminal whether the program runs in a terminal window boolean (2)NOYES
TerminalOptions if the program runs in a terminal, any options that should be passed to the terminal emulator before actually executing the program stringNONO
SwallowTitle if entry is swallowed onto the panel, this should be the title of window localestringNONO
SwallowExec program to exec if swallowed app is clicked stringNONO
MimeType the MIME type(s) supported by this entry regexp(s)NONO
Patterns if entry is type MimeType, various file name extensions associated with the MIME type. regexp(s)NONO
DefaultApp if entry is type MimeType, the default application associated with this mime type stringNONO
Dev if FSDevice type of entry, the device to mount stringNONO
FSType The type of filesystem to try to mount stringNONO
MountPoint if FSDevice type of entry, the mount point of the device in question stringNONO
ReadOnly if FSDevice type of entry, specifies whether or not the device is read-only boolean (2)NONO
UnmountIcon icon to display when device is not mounted Mounted devices display icon from Icon key stringNONO
SortOrder if entry of type Directory, this may specify the order in which to display files strings (3)NONO
URL if entry is Link type, the URL to access string NOYES

Notes:

  1. possible values are Application, Link, FSDevice, MimeType, Directory, Service, ServiceType

  2. historically these have been represented by the numeric entries 0 or 1. With this version of the standard they are now to be represented as a boolean string. However, if an implementation is reading a pre-1.0 desktop entry, it should interpret 0 and 1 as false and true, respectively.

  3. historically this has been a comma separated list. This is inconsistent with other lists which are separated by a semicolon. When reading a pre-1.0 desktop entry, comma separated lists should continue to be supported.

  4. while the version field is not required to be present, it should be in all newer implementations of the Desktop Entry specification. If the version number is not present, a "pre-standard" desktop entry file is to be assumed.


5. Character set encoding of the file

Desktop entry files are encoded as lines of 8-bit characters separated by LF characters.

Except for comments and values of type localestring, only ASCII characters are permitted in the file:

Comment lines are uninterpreted and may contain any character (except for LF). However, using UTF-8 for comment lines that contain characters not in ASCII is encouraged.

The encoding for values of type localestring is determined by the Encoding field of the desktop entry. This field should always be present. (However, many legacy files may not include it.)

Only two values for Encoding are currently defined: 'UTF-8', and 'Legacy-Mixed', and desktop files must not use any other value. Implementations must support the UTF-8 encoding, and may choose to support Legacy-Mixed in addition. For this reason, authors of desktop files are encouraged to use the value 'UTF-8'.

If the file specifies an unsupported encoding, the implementation should either ignore the file, or, if the user has requested a direct operation on the file (such as opening it for editing), display an appropriate error indication to the user.

In the absence of an Encoding line, the implementation may choose to autodetect the encoding of the file by using such factors as:

If the implementation does not perform such auto-detection, it should treat a file without an Encoding key in the same way as a file with an unsupported Encoding Key.


6. List of valid Exec parameter variables

Each "Exec" field may take a number of arguments which will be expanded by the file manager or program launcher and passed to the program if necessary. Recognized fields are as follows:

%f a single file name, even if multiple files are selected. The system reading the Desktop Entry should recognize that the program in question cannot handle multiple file arguments, and it should should probably spawn and execute multiple copies of a program for each selected file if the program is not able to handle additional file arguments. If files are not on the local file system (i.e. HTTP or FTP locations), the files will be copied to the local file system and %f will be expanded to point at the temporary file. Used for programs that do not understand URL syntax.
%F a list of files. Use for apps that can open several local files at once.
%u a single URL.
%U a list of URLs.
%d the directory of the file to open.
%D a list of directories
%n a single filename (without path)
%N a list of filenames (without path)
%i the icon associated with the desktop entry
%m the mini-icon associated with the desktop entry
%c the comment associated with the desktop entry
%k the name of the desktop file
%v the name of the Device entry in the desktop file


7. Detailed discussion of supporting MIME types

It is in every desktop's best interest to have thorough support for mime types. The old /etc/mailcap and /etc/mime.types files are rather limited in scope and frankly, are outdated. Various desktop systems have come up with different ways of extending this original system, but none are compatible with each other. The Desktop Entry Standard hopes to be able to provide the beginnings of a solution to this problem.

At a very basic level, the "Exec" key provides the default action to take when the program described by a desktop entry is used to open a document or data file. Usually this consists of some action along the lines of "kedit %f" or "ee %f". This is a good start, but it isn't as flexible as it can be.

Let us first establish that a program which supports a MIME type or multiple mime types may be able to support multiple actions on those MIME types as well. The desktop entry may want to define additional actions in addition to the default. The toplevel "Exec" key describes the default action; Let us define this action to also be known as the "Open" action. Additional actions which might be possible include View, Edit, Play, etc. A further revision of this document will probably specify several "standard" actions in addition to the default "Open" action, but in all cases, the number of actions is arbitrary.

Let us use a sound player as a simple example. Call it sp. The default Exec (Open) action for this program would likely look something like:

Exec=sp %u

However, imagine the sound player also supports editing of sound files in a graphical manner. We might wish to define an additional action which could accomodate this. Adding the action would be performed like this:

Actions=Edit;

[Desktop Action Edit]
Exec=sp -edit %u

As you can see, defining the action "edit" will enable an additional group of the name [Desktop Action actionname] to be read. This group can contain an additional Exec line, as well as possibly other information like a new Name, Comment, Icon, and Path. Thus right-clicking on a .wav file will show both the default "Open" action and this "Edit" action to both be displayed as choices in the context-menu. A left click (double or single, whichever the file manager implements) would cause the default action to take place. These are implementation-specific details which are up to the implementer, and are not enforced by this standard.

If no DefaultApp is specified for a particular MIME type, any one of the programs registered which claim to be able to handle the MIME type may become the default handler. This behaviour is undefined and implementation-specific. KDE doesn't use a DefaultApp anymore, but assigns a Preference number to each program, so that the highest number is the one chosen for handling the MIME type.


8. Extending the format

If the standard is to be amended with a new {key,value} pair which should be applicable to all supporting parties, a group discussion will take place. This is the preferred method for introducing changes. If one particular party wishes to add a field for personal use, they should prefix the key with the string "X-PRODUCT", i.e. "X-NewDesktop-Foo", following the precedent set by other IETF and RFC standards.

Alternatively, fields can be placed in their own group, where they may then have arbitrary key names. If this is the case, the group should follow the scheme outlined above, i.e. [X-PRODUCT GROUPNAME] or something similar. These steps will avoid namespace clashes between different yet similar environments.


A. Example Desktop Entry File

[Desktop Entry]
Version=1.0
Type=Application
Name=Foo Viewer
Comment=The best viewer for Foo objects available!
TryExec=fooview
Exec=fooview %F
Actions=Edit;Inverse
Icon=fooview.png
MimeType=image/x-foo
X-KDE-Library=libfooview
X-KDE-FactoryName=fooviewfactory
X-KDE-ServiceType=FooService

[Desktop Action Inverse]
Exec=fooview --inverse %f
Name=Foo Viewer (inverse image)

[Desktop Action Edit]
Exec=fooview --edit %f
Name=Foo Viewer (edit image)
Icon=fooview-edit.png

B. The Legacy-Mixed encoding

The Legacy-Mixed encoding corresponds to the traditional encoding of desktop files in older versions of the GNOME and KDE desktop files. In this encoding, the encoding of each localestring key is determined by the locale tag for that key, if any. For keys without a locale tag, the value must contain only ASCII characters.

If the locale tag includes an .ENCODING part, then that determines the encoding for the line. Otherwise, the encoding is determined by the language, or language-country pair from the locale, according to the following table.

EncodingTags
ARMSCII-8 (*)by
BIG5zh_TW.Big5
CP1251be bg
EUC-CNzh_CN.GB2312
EUC-JPja
EUC-KRko
GEORGIAN-ACADEMY (*)ka_GE.georgianacademy
GEORGIAN-PS (*)ka
ISO-8859-1br ca da de en es eu fi fr gl it nl wa no pt pt sv
ISO-8859-2cs hr hu pl ro sk sl sq sr
ISO-8859-3 eo
ISO-8859-5mk sp
ISO-8859-7el
ISO-8859-9tr
ISO-8859-13lt lv mi
ISO-8859-14ga cy
ISO-8859-15et
KOI8-Rru
KOI8-Uuk
TCVN-5712 (*)vi vi_VN.TCVN
TIS-620th

Encodings marked with a (*) are not currently supported by the GNU C Library; for this reason, implementations may choose to ignore lines in desktop files with the corresponding tags. Desktop files with these tags are currently rare or non-existent.

The encoding here is listed according to its canonical name in the GNU C Library's iconv facility. The more common tags tags found with an encoding part are listed here, so that implementors can verify that the correct encoding will be used. (In particular, note the mismatch between zh_CN.GB2312, and the canonical name EUC-CN.)