This is an experimental technologyCheck the Browser compatibility table carefully before using this in production.
The LargestContentfulPaint
interface of the Largest Contentful Paint API provides details about the largest image or text paint before user input on a web page. The timing of this paint is a good heuristic for when the main page content is available during load.
Properties
LargestContentfulPaint.element
- The element that is the current largest contentful paint.
LargestContentfulPaint.renderTime
- The time the element was rendered to the screen. May not be available if the element is a cross-origin image loaded without the
Timing-Allow-Origin
header. LargestContentfulPaint.loadTime
- The time the element was loaded.
LargestContentfulPaint.size
- The intrinsic size of the element returned as the area (width * height).
LargestContentfulPaint.id
- The id of the element. This property returns an empty string when there is no id.
LargestContentfulPaint.url
- If the element is an image, the request url of the image.
Methods
LargestContentfulPaint.toJSON()
- Returns the above properties as JSON.
Examples
The following example shows how to create a PerformanceObserver
that listens for largest-contentful-paint
entries and logs the LCP value to the console.
This example also demonstrates how to include buffered entries (those that ocurred before observer()
was called), which is done by setting the buffered
option to true
.
Note that in this example data is only sent to the server when the user leaves the tab.
// Catch errors since some browsers throw when using the new `type` option.
// https://bugs.webkit.org/show_bug.cgi?id=209216
try {
let lcp;
const po = new PerformanceObserver((entryList) => {
const entries = entryList.getEntries();
const lastEntry = entries[entries.length - 1];
// Update `lcp` to the latest value, using `renderTime` if it's available,
// otherwise using `loadTime`. (Note: `renderTime` may not be available on
// image elements loaded cross-origin without the `Timing-Allow-Origin` header.)
lcp = lastEntry.renderTime || lastEntry.loadTime;
});
po.observe({type: 'largest-contentful-paint', buffered: true});
// Send data to the server.
addEventListener('visibilitychange', function fn() {
if (lcp && document.visibilityState === 'hidden') {
console.log('LCP:', lcp);
removeEventListener('visibilitychange', fn, true);
}
}, true);
} catch (e) {
// Do nothing if the browser doesn't support this API.
}
Specifications
Specification | Status | Comment |
Largest Contentful PaintThe definition of 'LargestContentfulPaint' in that specification. | Editor's Draft | Initial definition. |
Browser compatibility
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 | |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 | |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 | |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 | |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 | |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 | |
Chrome
Full support 77 |
Edge
Full support 80 |
Firefox
No support No |
IE
No support No |
Opera
Full support Yes |
Safari
No support No |
WebView Android
Full support 77 |
Chrome Android
Full support 77 |
Firefox Android
No support No |
Opera Android
Full support Yes |
Safari iOS
No support No |
Samsung Internet Android
Full support 12.0 |
Legend
- Full support
- Full support
- No support
- No support
- Experimental. Expect behavior to change in the future.'
- Experimental. Expect behavior to change in the future.
LargestContentfulPaint by Mozilla Contributors is licensed under CC-BY-SA 2.5.