Navigator: requestMIDIAccess() method

{{APIRef("Web MIDI API")}} {{SecureContext_Header}}

The requestMIDIAccess() method of the {{domxref('Navigator')}} interface returns a {{jsxref('Promise')}} representing a request for access to MIDI devices on a user’s system. This method is part of the Web MIDI API, which provides a means for accessing, enumerating, and manipulating MIDI devices.

This method may prompt the user for access to MIDI devices available to their system, or it may use a previously established preference to grant or deny access. If permission is granted then the {{jsxref('Promise')}} resolves and a MIDIAccess object is returned.

Syntax

requestMIDIAccess()
requestMIDIAccess(MIDIOptions)

Parameters

MIDIOptions {{optional_inline}}
- : An {{jsxref('Object')}} representing options to pass into the method. These options are:
  - sysex
    - : A {{jsxref('Boolean')}} value that, if set to true, allows the ability to send and receive system exclusive (sysex) messages. The default value is false.
  - software
    - : A {{jsxref('Boolean')}} value that, if set to true, allows the system to utilize any installed software synthesizers. The default value is false.

Return value

A {{jsxref('Promise')}} that resolves with a MIDIAccess object.

Exceptions

AbortError {{domxref("DOMException")}}
- : Thrown if the document or page is closed due to user navigation.
InvalidStateError {{domxref("DOMException")}}
- : Thrown if the underlying system raises any errors.
NotSupportedError {{domxref("DOMException")}}
- : Thrown if the feature or options are not supported by the system.
SecurityError {{domxref("DOMException")}}
- : Thrown if the user or system denies the application from creating a MIDIAccess object with the requested options, or if the document is not allowed to use the feature (for example, because of a Permission Policy, or because the user previously denied a permission request).

Security requirements

Access to the API is subject to the following constraints:

The method must be called in a secure context.
Access may be gated by the midi HTTP Permission Policy.
The user must explicitly grant permission to use the API though a user-agent specific mechanism, or have previously granted permission. Note that if access is denied by a permission policy it cannot be granted by a user permission.

The permission status can be queried using the Permissions API method navigator.permissions.query(), passing a permission descriptor with the midi permission and (optional) sysex property:

navigator.permissions.query({ name: "midi", sysex: true }).then((result) => {
  if (result.state === "granted") {
    // Access granted.
  } else if (result.state === "prompt") {
    // Using API will prompt for permission
  }
  // Permission was denied by user prompt or permission policy
});

Examples

Request MIDI access

In the following example, the Navigator.requestMIDIAccess() method returns the {{domxref("MIDIAccess")}} object, which gives access to information about the input and output MIDI ports.

navigator.requestMIDIAccess().then((access) => {
  // Get lists of available MIDI controllers
  const inputs = access.inputs.values();
  const outputs = access.outputs.values();
  // …
});

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

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