### Function

# Gio Application id_is_valid

since: 2.28

#### Declaration

    gboolean
    g_application_id_is_valid (
      const gchar* application_id
    )

#### Description

Checks if `application_id` is a valid application identifier.

A valid ID is required for calls to `g_application_new()` and g_application_set_application_id().

Application identifiers follow the same format as D-Bus well-known bus names. For convenience, the restrictions on application identifiers are reproduced here:

- Application identifiers are composed of 1 or more elements separated by a period (`.`) character. All elements must contain at least one character.

- Each element must only contain the ASCII characters `[A-Z][a-z][0-9]_-`, with `-` discouraged in new application identifiers. Each element must not begin with a digit.

- Application identifiers must contain at least one `.` (period) character (and thus at least two elements).

- Application identifiers must not begin with a `.` (period) character.

- Application identifiers must not exceed 255 characters.

Note that the hyphen (`-`) character is allowed in application identifiers, but is problematic or not allowed in various specifications and APIs that refer to D-Bus, such as Flatpak application IDs, the `DBusActivatable` interface in the Desktop Entry Specification, and the convention that an application’s “main” interface and object path resemble its application identifier and bus name. To avoid situations that require special-case handling, it is recommended that new application identifiers consistently replace hyphens with underscores.

Like D-Bus interface names, application identifiers should start with the reversed DNS domain name of the author of the interface (in lower-case), and it is conventional for the rest of the application identifier to consist of words run together, with initial capital letters.

As with D-Bus interface names, if the author’s DNS domain name contains hyphen/minus characters they should be replaced by underscores, and if it contains leading digits they should be escaped by prepending an underscore. For example, if the owner of 7-zip.org used an application identifier for an archiving application, it might be named `org._7_zip.Archiver`.

Available since: 2.28

#### Parameters

`application_id`

  Type: `const gchar*`

  A potential application identifier.

  The data is owned by the caller of the function.
  The value is a NUL terminated UTF-8 string.

#### Return value

Type: `gboolean`

`TRUE` if `application_id` is valid.