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Recognized desktop entry keys

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.

Some keys only make sense in the context when another particular key is also present and set to a specific value. Those keys should not be used if the particular key is not present or not set to the specific value. For example, the Terminal key can only be used when the value of the Type key is Application.

If a REQUIRED key is only valid in the context of another key set to a specific value, then it has to be present only if the other key is set to the specific value. For example, the URL key has to be present when and only when when the value of the Type key is Link.

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

Table 2. Standard Keys

KeyDescriptionValue TypeREQ?Type
Type This specification defines 3 types of desktop entries: Application (type 1), Link (type 2) and Directory (type 3). To allow the addition of new types in the future, implementations should ignore desktop entries with an unknown type. string YES
Version Version of the Desktop Entry Specification that the desktop entry conforms with. Entries that confirm with this version of the specification should use 1.0. Note that the version field is not required to be present. string NO 1-3
Name Specific name of the application, for example "Mozilla". localestring YES 1-3
GenericName Generic name of the application, for example "Web Browser". localestring NO 1-3
NoDisplay NoDisplay means "this application exists, but don't display it in the menus". This can be useful to e.g. associate this application with MIME types, so that it gets launched from a file manager (or other apps), without having a menu entry for it (there are tons of good reasons for this, including e.g. the netscape -remote, or kfmclient openURL kind of stuff). boolean NO 1-3
Comment Tooltip for the entry, for example "View sites on the Internet". The value should not be redundant with the values of Name and GenericName. localestring NO 1-3
Icon Icon to display in file manager, menus, etc. If the name is an absolute path, the given file will be used. If the name is not an absolute path, the algorithm described in the Icon Theme Specification will be used to locate the icon. localestringNO1-3
Hidden Hidden should have been called Deleted. It means the user deleted (at his level) something that was present (at an upper level, e.g. in the system dirs). It's strictly equivalent to the .desktop file not existing at all, as far as that user is concerned. This can also be used to "uninstall" existing files (e.g. due to a renaming) - by letting make install install a file with Hidden=true in it. booleanNO1-3
OnlyShowIn, NotShowIn A list of strings identifying the environments that should display/not display a given desktop entry. Only one of these keys, either OnlyShowIn or NotShowIn, may appear in a group (for possible values see the Desktop Menu Specification). string(s)NO1-3
TryExec Path to an executable file on disk used to determine if the program is actually installed. If the path is not an absolute path, the file is looked up in the $PATH environment variable. If the file is not present or if it is not executable, the entry may be ignored (not be used in menus, for example). stringNO1
Exec Program to execute, possibly with arguments. stringYES1
Path If entry is of type Application, the working directory to run the program in. stringNO1
Terminal Whether the program runs in a terminal window. booleanNO1
MimeType The MIME type(s) supported by this application. string(s)NO1
Categories Categories in which the entry should be shown in a menu (for possible values see the Desktop Menu Specification). string(s)NO1
StartupNotify If true, it is KNOWN that the application will send a "remove" message when started with the DESKTOP_STARTUP_ID environment variable set. If false, it is KNOWN that the application does not work with startup notification at all (does not shown any window, breaks even when using StartupWMClass, etc.). If absent, a reasonable handling is up to implementations (assuming false, using StartupWMClass, etc.). (See the Startup Notification Protocol Specification for more details). booleanNO1
StartupWMClass If specified, it is known that the application will map at least one window with the given string as its WM class or WM name hint (see the Startup Notification Protocol Specification for more details). stringNO1
URL If entry is Link type, the URL to access. stringYES2

The Exec key

The Exec key must contain a command line. A command line consists of an executable program optionally followed by one or more arguments. The executable program can either be specified with its full path or with the name of the executable only. If no full path is provided the executable is looked up in the $PATH environment variable used by the desktop environment. The name or path of the executable program may not contain the equal sign ("="). Arguments are separated by a space.

Arguments may be quoted in whole. If an argument contains a reserved character the argument must be quoted. The rules for quoting of arguments is also applicable to the executable name or path of the executable program as provided.

Quoting must be done by enclosing the argument between double quotes and escaping the double quote character, backtick character ("`"), dollar sign ("$") and backslash character ("\") by preceding it with an additional backslash character. Implementations must undo quoting before expanding field codes and before passing the argument to the executable program. Reserved characters are space (" "), tab, newline, double quote, single quote ("'"), backslash character ("\"), greater-than sign (">"), less-than sign ("<"), tilde ("~"), vertical bar ("|"), ampersand ("&"), semicolon (";"), dollar sign ("$"), asterisk ("*"), question mark ("?"), hash mark ("#"), parenthesis ("(") and (")") and backtick character ("`").

Note that the general escape rule for values of type string states that the backslash character can be escaped as ("\\") as well and that this escape rule is applied before the quoting rule. As such, to unambiguously represent a literal backslash character in a quoted argument in a desktop entry file requires the use of four successive backslash characters ("\\\\"). Likewise, a literal dollar sign in a quoted argument in a desktop entry file is unambiguously represented with ("\\$").

A number of special field codes have been defined which will be expanded by the file manager or program launcher when encountered in the command line. Field codes consist of the percentage character ("%") followed by an alpha character. Literal percentage characters must be escaped as %%. Deprecated field codes should be removed from the command line and ignored. Field codes are expanded only once, the string that is used to replace the field code should not be checked for field codes itself.

Command lines that contain a field code that is not listed in this specification are invalid and must not be processed, in particular implementations may not introduce support for field codes not listed in this specification. Extensions, if any, should be introduced by means of a new key.

Implementations must take care not to expand field codes into multiple arguments unless explicitly instructed by this specification. This means that name fields, filenames and other replacements that can contain spaces must be passed as a single argument to the executable program after expansion.

Although the Exec key is defined to have a value of the type string, which is limited to ASCII characters, field code expansion may introduce non-ASCII characters in arguments. Implementations must take care that all characters in arguments passed to the executable program are properly encoded according to the applicable locale setting.

Recognized field codes 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. are on 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 the URL syntax.
%F A list of files. Use for apps that can open several local files at once. Each file is passed as a separate argument to the executable program.
%u A single URL. Local files may either be passed as file: URLs or as file path.
%U A list of URLs. Each URL is passed as a separate argument to the executable program. Local files may either be passed as file: URLs or as file path.
%d Deprecated.
%D Deprecated.
%n Deprecated.
%N Deprecated.
%i The Icon key of the desktop entry expanded as two arguments, first --icon and then the value of the Icon key. Should not expand to any arguments if the Icon key is empty or missing.
%c The translated name of the application as listed in the appropriate Name key in the desktop entry.
%k The location of the desktop file as either a URI (if for example gotten from the vfolder system) or a local filename or empty if no location is known.
%v Deprecated.
%m Deprecated.

A command line may contain at most one %f, %u, %F or %U field code. If the application should not open any file the %f, %u, %F and %U field codes must be removed from the command line and ignored.

Field codes must not be used inside a quoted argument, the result of field code expansion inside a quoted argument is undefined. The %F and %U field codes may only be used as an argument on their own.

Registering MIME Types

The MimeType key is used to indicate the MIME Types that an application knows how to handle. It is expected that for some applications this list could become long. An application is expected to be able to reasonably open files of these types using the command listed in the Exec key.

There should be no priority for MIME Types in this field, or any form of priority in the desktop file. Priority for applications is handled external to the .desktop files.

C. Deprecated Items

As this standard is quite old there are some deprecated items that may or may not be used by several implementations.