Setting default applications per file type involves detection of the file type as the first step. Since the application launcher cannot fully understand all file types, the detection is based on reading only a small part of the file. There are two common ways to determine the file type:
- using the file name extension, for example .html or .jpeg
- using the so-called "magic bytes" at the start of the file
The first method is very simple and fast, but inaccurate if the file is not named "correctly". The second is more accurate, but slower.
Since files are not required to have an extension and multiple file name extensions can be used for the same file type, MIME types are commonly used instead to uniquely represent the type of a file. In Arch, tools from the package are used to maintain the MIME type database, which is used by other packages to register new MIME types. Each package can also use the Desktop entries to provide information about the MIME types that can be handled by the packaged software. There is frequently more than one application able to handle data of a certain MIME type, so users and even some packages (e.g. desktop environments) assemble lists of default applications for each MIME type.
Note that while Arch Linux does not provide custom presets for default applications, the desktop environment you install may do so. Some desktop environments also provide a GUI or a file-manager which enables to interactively configure default applications for certain file extensions. If this suffices for your system usage, you may not need to configure anything further.
- 1 MIME types and desktop entries
- 2 Set default applications
- 3 Utilities to manage MIME types
- 4 Troubleshooting
MIME types and desktop entries
MIME-types are specified by two slash (
/) parts: Type/Extension, for example
video/x-ms-wmv. The second part of the MIME-type is expanding faster, for example with new applications or data encoding standards.
The default applications to open a MIME-type are usually stored in mimeapps.list files, but some programs store MIME-type associations in their own custom configuration files. If a MIME-type association is not found in the default configuration, the program should look for the first match of the MIME-type in .desktop files.
Description of some MIME-type first part and examples of second parts:
|Type of MIME (1st part)||Description||Examples of extension (2nd part)|
|application||Files with binary content such, e.g.: documents,archives,...||epub+zip, ereader, excel, gbr, gzip|
|audio||Audio files that that can be played by a music player or audio editor||flac, m4a, midi|
|chemical||Chemical information, molecular and other chemical data||x-cif, x-cml, x-daylight-smiles, x-gamess-input, x-gamess-output, x-gaussian-checkpoint, x-gaussian-cube, x-gaussian-log, x-mopac-out, x-pdb, x-qchem-output, x-xyz|
|image||Image files that can be opened by image editor or image viewer||bmp, crw, g3fax, gif, jp2, jpeg, jpeg2000, jpg|
|inode||Can be opened by a file manager||blockdevice, chardevice, directory, fifo, mount-point, socket, symlink|
|message||Message protocols||delivery-status, disposition-notification, external-body, news, partial, rfc822, x-gnu-rmail|
|misc||Streaming meta data||ultravox|
|video||Video files that can be played or edited with a video editor||flv, mp2t, mp4|
|x-content||Content on disks such as e.g. Audio,Video,Image or blank disk||audio-cdda, audio-player, blank-bd, blank-cd, blank-dvd, blank-hddvd, image-picturecd, video-dvd, video-svcd, video-vcd|
|x-scheme-handler||Internet protocol||ftp, geo, ghelp, help, http, https, hwplay, icy, icyx, info, irc, magnet, mailto, man, mms, mmsh, net, pnm, rtmp, rtp, rtsp, skype, uvox, vnc, xmpp|
|multipart||Multi-part mime messages||alternative, appledouble, digest, encrypted, mixed, related, report, signed, x-mixed-replace|
|model||such as 3D model||x-kpovmodeler, vrml, x-modelica|
For the description of MIME-types you can search in XDG database:
$ grep -e 'mime-type type=' -e '<comment>' /usr/share/mime/packages/freedesktop.org.xml
If you ever require to create a custom association of a new file extension to a MIME-type, see the the short #Example: .xml and related .desktop configuration and the Association between MIME types and applications standard.
Set default applications
In order to set a default application, you need to
- decide which of the #Default mimeapps.list files is applicable for your case and,
- change the #Configuration of the mimeapps.list file accordingly.
Any manual configuration of the #Shared MIME-info database is only required, if the application is not setup correctly or desktop does not comply to the standard yet.
Default mimeapps.list files
mimeapps.list file stores the configuration for the default application to open a MIME-type.
There are different locations for it:
- custom locations used by some programs.
$desktop in the following list denotes the name of the related desktop environment or window manager. The search order of paths is:
||user overrides, desktop-specific|
||sysadmin and vendor overrides, desktop-specific|
||sysadmin and vendor overrides|
||for compatibility but now deprecated, desktop-specific|
||for compatibility but now deprecated|
||distribution-provided defaults, desktop-specific|
Configuration of the mimeapps.list file
The file contains two main sections for default and additional alternatives to open files of a MIME-type. The second and the third section (
[Removed Associations]) are optional.
If the application installed a correct desktop entry file (examples used below
foo1.desktop, etc.), it contains the registered MIME-types it can handle. To set a default application, all you need to do is adjust the associations in the respective
mimeapps.list (see also the freedesktop specification).
For example, the following sets
default1.desktop to open
[Default Applications] mimetype1=default1.desktop
Defined additional associations of applications to MIME-types (these might appear in file manager Open with GUI, for example):
[Added Associations] mimetype1=foo1.desktop;foo2.desktop;foo3.desktop; mimetype2=foo4.desktop;
Removed associations of applications with MIME-types (blacklisting a MIME-type association of an application in its .desktop file):
[Removed Associations] mimetype1=foo5.desktop
Multiple .desktop files for a single MIME-type must be semicolon-separated. Not supported entries are ignored in
mimeapps.list. The DE/WM then searches for the first match to the needed MIME-type them in the default path for .desktop files.
Your choice of desktop environment, or none, will affect how your default applications are associated. Further, note that some packages use additional work-around presets, for example Mozilla's packages install a
In background to the
mimeapps.list files, the system holds a database of MIME-type information registered via the installed applications' .desktop files, the Shared MIME-info Database. It is created automatically as soon as an application depending on it is installed, via the following pacman#Hooks:
- updates the MIME-info database in
/usr/share/mime, in particular also the .xml specification in
/usr/share/mime/packages/freedesktop.org.xmlfor the MIME-types standards
- updates the
mimeinfo.cachelocated (per default) in
These files keep track of which MIME-types are associated with which .desktop files overall. When an application is installed, updated or removed, the pacman hooks keep the database updated accordingly.
Application specific configuration is stored in .xml files and further files of the database (see .xml source files) are stored in .keys and .mime files that are located in
Global directories for the .xml files are:
Any user-specific .xml configuration may be stored in:
The following is a short example to create files to associate an application with a MIME-type. It only needs to be followed, if the application has not setup and registered its configuration sufficiently.
User-specific paths are used to override system defaults, while keeping the integrity of the rest of the system-wide configuration.
Create and edit
<?xml version="1.0" encoding="UTF-8"?> <mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info"> <mime-type type="application/x-foobar"> <comment>foo file</comment> <icon name="application-x-foobar"/> <glob-deleteall/> <glob pattern="*.foo"/> </mime-type> </mime-info>
Create a related desktop entry file:
[Desktop Entry] Name=Foobar Exec=/usr/bin/foobar MimeType=application/x-foobar Icon=foobar Terminal=false Type=Application Categories=AudioVideo;Player;Video; Comment=
Now update the application and mime database with:
$ update-desktop-database ~/.local/share/applications $ update-mime-database ~/.local/share/mime
Programs that use MIME-types, such as file managers, should now open
*.foo files with foobar (you may need to restart your file manager to see the change.)
See also Environment variables#Examples about global variables that can be used in start-up scripts to set default applications for specific actions.
Utilities to manage MIME types
Many of the file managers has options to set up and configure associations of mime types with programs.
It can be done by using:
- Preferences for selected file
- File manager configuration menu
- External program for a specific file manager
Other utilities to manage MIME-types are:
|Name/Package||Method||Based on||xdg-utils replacement||Configuration file|
|MIME-type||Utility for ROX applications|
custom is optional
| SQLite database
|xdg-open|| custom SQLite database |
Examples of usage
Here is a short description about how to use command line tools to show MIME-type of a file or set preferred program as default to open MIME-type.
Tools detecting MIME-type by reading meta-data from header of the file or detecting by magic number that is in two bytes identifier in the begin of the file. See File header.
Many programs are using command file to detect correct MIME-type. For detection it uses compiled database that is stored in the
/usr/share/misc/magic/ directory. It has many options to determinate correct MIME-type and for showing output.
In Linux it is two standards to detect MIME-type that can affect which program will start and open the file, e.g. extension is associated with one program but content is associated with another MIME-type. The simplest way to see what is your system prioritizes is by renaming file extension and check again with tools that can use custom *.xml configuration files.
Here is examples of utility xdg-mime that first checking association of extension in *.xml configuration files.
|Without extension||With extension|
|xdg-mime query filetype foo-file||xdg-mime query filetype foo-file.jpg|
Comparison functionality of the tools
Here is shown options only for simple or multiple checks of a file, for more options read their own documentation.
|file||(has many)||Magic(Byte/Pattern)||Show only||binary||terminal|
|xdg-mime||query filetype||*.xml -> Magic||Show / Set||script||terminal|
|mimetype||-i (*.xml) -M (Magic)||*.xml -> Magic||Show only||script||terminal|
|mimeo||-m||*.xml -> Magic||Show / Set / Launch||script||terminal|
Set use of MIME-type by default
Comparison functionality of the tools
Here is shown options only for single file associations, for more options read their own documentation.
|xdg-mime||default *.desktop Type1/Extension1 Type2/Extension2||Show / Set||script||terminal|
|mimeo||--prefer 'regex:^Type/(Extension1 |Extension?2)$' *.desktop||Show / Set / Launch||script||terminal|
|mimeopen||--ask-default (interactive)||Set / Launch||script||terminal|
xdg-open (from the desktop environment is detected. It is a desktop-independent tool. Many applications invoke the
xdg-open command internally. Inside a desktop environment it passes the arguments to desktop supported environment's file-opener applications (e.g. gvfs-open, kde-open, or exo-open). When no desktop environment is detected the xdg-open will use its own configuration files.
mimeopen (from thepackage) can launch applications from command line. It can use custom database and prompt user to chose default application from a list of detected relevant and offers to chose own alternative.
Example of the prompt:
$ mimeopen -d /path/to/foo-file
Please choose a default application for files of type Type/Extension 1) notepad (wine-extension-txt) 2) Leafpad (leafpad) 3) OpenOffice.org Writer (writer) 4) gVim (gvim) 5) Other...
Your answer becomes the default handler for that type of file. Mimeopen is installed as
If you run xdg-open without a desktop environment, you should also install AUR for a faster alternative., or AUR and AUR from the
The mailcap file.
The .mailcap file format is used by mail programs such as
*/*; xdg-open "%s"
Extended practical examples
xdg-mime modifies the local file
To query the mime type used by an existing file, use
$ xdg-mime query filetype file.ext
To change an associated desktop entry by setting Thunar as the default file browser:
$ xdg-mime default Thunar.desktop inode/directory
Note that you should not specify the complete path, but only the name of the .desktop file.
This command can take multiple mime-types, allowing related files to be handled by the same program. The example below associates Emacs to all known source files:
$ xdg-mime default emacs.desktop $(grep '^text/x-*' /usr/share/mime/types)
Set the default browser
To set the default application for
http(s):// internet protocols:
$ xdg-mime default midori.desktop x-scheme-handler/http $ xdg-mime default midori.desktop x-scheme-handler/https
As an alternative try:
$ xdg-settings set default-web-browser netsurf.desktop
To verify if the URLs opens correctly:
$ xdg-open https://archlinux.org
To associate .html files with theweb-browser:
$ xdg-mime default netsurf.desktop text/html
Variables in .desktop files that affect application launch
Desktop environments and file managers supporting the specifications launch programs according to definition in the .desktop files. See Desktop entries#Application entry.
Usually, configuration of the packaged .desktop files is not required, but it may not be bug-free. Even if an application containing necessary MIME-type description in the .desktop file
MimeType variable that is used for association, it can fail to start correctly, not start at all or start without opening a file.
This may happen, for example, if the
Exec variable is missing internal options needed for how to open a file, or how the application is shown in the menu. The
Exec variable usually begins with
%; for its currently supported options, see exec-variables.
The following table lists the main variable entries of .desktop files that affect how an application starts, if it has a MIME-type associated with it.
|Variable names||Example 1 content||Example 2 content||Description|
|DBusActivatable||DBusActivatable=true||DBusActivatable=false|| Application interact with D-Bus. |
See also configuration: D-Bus.
|MimeType||MimeType=application/vnd.oasis.opendocument.text||MimeType=application/vnd.sun.xml.math||List of MIME types supported by application|
|StartupWMClass||StartupWMClass=google-chrome||StartupWMClass=xpad||Associate windows with the owning application|
|Terminal||Terminal=true||Terminal=false||Start in default terminal|