Choosing Applications to Handle Files

What Are MIME Types?

MIME types are a standard way to identify files so that they can be easily transmitted over the Internet. MIME stands for "Multipurpose Internet Mail Extention." Each type of file is assigned a specific MIME type. For instance, the MIME type for HTML files is "text/html," and the MIME type for JPEG files is "image/jpeg." A file's MIME type tells Internet applications such as browsers and email programs what type of file is being exchanged, how to encode it for transmission, and how to decode it when it arrives at its destination.

Unless you've specified that a particular application or viewer should open a file, it normally opens automatically in an application that's appropriate for the type. For instance, a JPEG file normally opens automatically in a graphics application.

You can choose which application or viewer opens automatically for a particular type of file. You can also set up new applications to handle particular types of files.

Adding and Removing Applications

When you select a file and choose Open With, you see a list of applications that can open that particular file. You also have the choices Other Application and Other Viewer, which let you use an application that's not in the list to open or view the file.

You can modify the list of applications you see when you choose Open With:

1. Click the icon of the file for which you want to change the Open With options.

2. Open the File menu and choose Open With->Other Application. A dialog box opens that lists all the applications currently able to open this particular type of file. Some applications in the list are tagged "in the menu" for this file type; others are tagged "not in the menu."

3. Select an application in the list and click Modify.

4. Choose the option you want. You can choose to add or remove the application from the menu for this particular file or for all files of this type.

5. Click OK.

6. Click Done. (If you want to open the file now, click Choose.)

To modify the list of viewers you see when you choose Open With, follow steps 1 through 6 above but choose Other Viewer instead of Other Application in step 2. (A viewer lets you view but not edit a file. Opening a file in a viewer can save time and memory.)

Changing the Default Application

The default application or viewer opens a file automatically when you select the file and choose Open from the File menu. To specify the default:

1. Click the icon of the file for which you want to change the default.

2. Open the File menu and choose Open With->Other Application

3. Select the application you want to use as the default and click Modify.

4. Choose the option you want. You can choose to use the application as the default for this particular file or for all files of this type.

5. Click OK.

6. Click Done. (If you want to open the file now, click Choose.)

To change the default viewer, follow steps 1 through 6 above, but choose Other Viewer instead of Other Application in step 2.

Configuring Additional Applications (Advanced)

The Open With Other dialog box (described above) lists all the applications that Nautilus can currently use to open a file. Your computer may have additional applications that can open the file but that aren't in the list. You can configure additional applications so that they appear in the list:

1. Click to select the file for which you want to configure a new application.

2. Open the File menu and choose Open With->Other Application

3. In the File Types and Programs section, click Go There. The GNOME Control Center opens, with the File Types and Programs preferences displayed.

4. In the list, find the file type for the file you're working with. For instance, if you're configuring an additional application for a text file, locate the entry for text files in the list. (Clicking the column headers sorts the list.)

5. Once you've found the file type, click to select it.

6. In the Default Action section, click Edit List.

7. Click Add Application.

8. Type the application's name and the command that launches the application. The command is the same as the command you'd type if you were launching the application from a GNOME terminal window.

9. Click OK in each of the next three dialog boxes to dismiss them.

To edit the name or command for an application, follow steps 1 through 9 but click Edit Application instead of Add Application in step 7.

To remove an application, follow steps 1 through 7 but click Delete Application instead of Add Application in step 7.

Adding a New MIME Type (Advanced)

You can set up default applications for new file types that are not currently configured on your system.

First, add the new file type:

1. Open the GNOME Main Menu and choose Programs->Settings->GNOME Control Center.

2. Choose File Types and Programs in the GNOME Control Center's left-hand column.

3. Click Add New MIME Type.

4. In the Add MIME Type dialog box, enter the MIME type and a description. For instance, if you have a new kind of image file of type alf (for alfie files), you'd enter image/x-alf as the MIME type and Alfie image as the description.

5. Click OK. Your new MIME type is added to the list.

Second, associate a file extension:

1. Select your new MIME type in the list and click Change File Extensions.

2. Click Add.

3. Type a file extension (for instance, .alf for the alfie image files in the example) and click OK.

4. Click OK.

Third, specify an icon:

1. Select your new MIME type in the list and click Change Icon.

2. Choose an icon and click OK.

Fourth, define the application(s) that can open files of this type:

1. Select your new MIME type in the list.

2. In the Default Action section, click Edit List.

3. Click Add Application.

4. Type the application's name and the command that launches the application. The command is the same as the command you'd type if you were launching the application from a GNOME terminal window.

5. Click OK in each of the next three dialog boxes to dismiss them.