MediaRecorder

The MediaRecorder interface of the MediaStream Recording API provides functionality to easily record media. It is created using the MediaRecorder() constructor.

Constructor

MediaRecorder()

Creates a new MediaRecorder object, given a MediaStream to record. Options are available to do things like set the container's MIME type (such as "video/webm" or "video/mp4") and the bit rates of the audio and video tracks or a single overall bit rate.

Instance properties

MediaRecorder.mimeType Read only

Returns the MIME type that was selected as the recording container for the MediaRecorder object when it was created.

MediaRecorder.state Read only

Returns the current state of the MediaRecorder object (inactive, recording, or paused.)

MediaRecorder.stream Read only

Returns the stream that was passed into the constructor when the MediaRecorder was created.

MediaRecorder.videoBitsPerSecond Read only

Returns the video encoding bit rate in use. This may differ from the bit rate specified in the constructor (if it was provided).

MediaRecorder.audioBitsPerSecond Read only

Returns the audio encoding bit rate in use. This may differ from the bit rate specified in the constructor (if it was provided).

MediaRecorder.audioBitrateMode Read only Experimental

Returns the bitrate mode used to encode audio tracks.

Static methods

MediaRecorder.isTypeSupported()

A static method which returns a true or false value indicating if the given MIME media type is supported by the current user agent.

Instance methods

MediaRecorder.pause()

Pauses the recording of media.

MediaRecorder.requestData()

Requests a Blob containing the saved data received thus far (or since the last time requestData() was called. After calling this method, recording continues, but in a new Blob.

MediaRecorder.resume()

Resumes recording of media after having been paused.

MediaRecorder.start()

Begins recording media; this method can optionally be passed a timeslice argument with a value in milliseconds. If this is specified, the media will be captured in separate chunks of that duration, rather than the default behavior of recording the media in a single large chunk.

MediaRecorder.stop()

Stops recording, at which point a dataavailable event containing the final Blob of saved data is fired. No more recording occurs.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

dataavailable

Fires periodically each time timeslice milliseconds of media have been recorded (or when the entire media has been recorded, if timeslice wasn't specified). The event, of type BlobEvent, contains the recorded media in its data property.

error

Fired when there are fatal errors that stop recording. The received event is based on the MediaRecorderErrorEvent interface, whose error property contains a DOMException that describes the actual error that occurred.

pause

Fired when media recording is paused.

resume

Fired when media recording resumes after being paused.

start

Fired when media recording starts.

stop

Fired when media recording ends, either when the MediaStream ends, or after the MediaRecorder.stop() method is called.

Example

if (navigator.mediaDevices) {
  console.log("getUserMedia supported.");

  const constraints = { audio: true };
  let chunks = [];

  navigator.mediaDevices
    .getUserMedia(constraints)
    .then((stream) => {
      const mediaRecorder = new MediaRecorder(stream);

      record.onclick = () => {
        mediaRecorder.start();
        console.log(mediaRecorder.state);
        console.log("recorder started");
        record.style.background = "red";
        record.style.color = "black";
      };

      stop.onclick = () => {
        mediaRecorder.stop();
        console.log(mediaRecorder.state);
        console.log("recorder stopped");
        record.style.background = "";
        record.style.color = "";
      };

      mediaRecorder.onstop = (e) => {
        console.log("data available after MediaRecorder.stop() called.");

        const clipName = prompt("Enter a name for your sound clip");

        const clipContainer = document.createElement("article");
        const clipLabel = document.createElement("p");
        const audio = document.createElement("audio");
        const deleteButton = document.createElement("button");
        const mainContainer = document.querySelector("body");

        clipContainer.classList.add("clip");
        audio.setAttribute("controls", "");
        deleteButton.textContent = "Delete";
        clipLabel.textContent = clipName;

        clipContainer.appendChild(audio);
        clipContainer.appendChild(clipLabel);
        clipContainer.appendChild(deleteButton);
        mainContainer.appendChild(clipContainer);

        audio.controls = true;
        const blob = new Blob(chunks, { type: "audio/ogg; codecs=opus" });
        chunks = [];
        const audioURL = URL.createObjectURL(blob);
        audio.src = audioURL;
        console.log("recorder stopped");

        deleteButton.onclick = (e) => {
          const evtTgt = e.target;
          evtTgt.parentNode.parentNode.removeChild(evtTgt.parentNode);
        };
      };

      mediaRecorder.ondataavailable = (e) => {
        chunks.push(e.data);
      };
    })
    .catch((err) => {
      console.error(`The following error occurred: ${err}`);
    });
}

Specifications

Browser compatibility

See also

• Using the MediaStream Recording API
• Web Dictaphone: MediaRecorder + getUserMedia + Web Audio API visualization demo, by Chris Mills (source on GitHub.)
• Recording a media element
• simpl.info MediaStream Recording demo, by Sam Dutton.
• MediaDevices.getUserMedia()
• OpenLang: HTML video language lab web application using MediaDevices and the MediaStream Recording API for video recording (source on GitHub)