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HTMLMediaElement: loadstart event

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

The loadstart event is fired when the browser has started to load a resource.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("loadstart", (event) => { })

onloadstart = (event) => { }

Event type

A generic Event.

Examples

Live example

HTML

<div class="example">
  <button type="button">Load video</button>
  <video controls width="250"></video>

  <div class="event-log">
    <label for="eventLog">Event log:</label>
    <textarea readonly class="event-log-contents" id="eventLog"></textarea>
  </div>
</div>

JavaScript

const loadVideo = document.querySelector("button");
const video = document.querySelector("video");
const eventLog = document.querySelector(".event-log-contents");
let source = null;

function handleEvent(event) {
  eventLog.textContent += `${event.type}\n`;
}

video.addEventListener("loadstart", handleEvent);
video.addEventListener("progress", handleEvent);
video.addEventListener("canplay", handleEvent);
video.addEventListener("canplaythrough", handleEvent);

loadVideo.addEventListener("click", () => {
  if (source) {
    document.location.reload();
  } else {
    loadVideo.textContent = "Reset example";
    source = document.createElement("source");
    source.setAttribute("src", "/shared-assets/videos/flower.webm");
    source.setAttribute("type", "video/webm");

    video.appendChild(source);
  }
});

Result

Specifications

Specification
HTML> # event-media-loadstart>
HTML> # handler-onloadstart>

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS
`loadstart_event`	3	12	6	≤12.1	4	18	6	≤12.1	3	1.0	4.4	3