# How to measure the time-to-first-frame on Web

The time-to-first-frame, also known as the start-up time, is the time between the moment where playback is requested and the moment where the first frame is rendered.

To measure it, measure the time between the `play` event and the `playing` event.

## Usage

```js
let playEventRegisteredAt;

function playEventHandler() {
  player.removeEventListener('play', playEventHandler);
  playEventRegisteredAt = Date.now();
}

function playingEventHandler() {
  player.removeEventListener('playing', playingEventHandler);
  const timeToFirstFrame = Date.now() - playEventRegisteredAt;
  console.log('Time-to-first-frame:', timeToFirstFrame);
}

player.addEventListener('play', playEventHandler);
player.addEventListener('playing', playingEventHandler);
```