PerformanceServerTiming: toJSON() method

Baseline 2023
Newly available

Since March 2023, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

Note: This feature is available in Web Workers.

The toJSON() method of the PerformanceServerTiming interface is a serializer; it returns a JSON representation of the PerformanceServerTiming object.

Syntax

js
toJSON()

Parameters

None.

Return value

A JSON object that is the serialization of the PerformanceServerTiming object.

Examples

Logging server timing entries

Server timing metrics require the server to send the Server-Timing header. For example:

http
Server-Timing: cache;desc="Cache Read";dur=23.2

The serverTiming entries can live on navigation and resource entries.

Example using a PerformanceObserver, which notifies of new navigation and resource performance entries as they are recorded in the browser's performance timeline. Use the buffered option to access entries from before the observer creation.

js
const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    entry.serverTiming.forEach((serverEntry) => {
      console.log(serverEntry.toJSON());
    });
  });
});

["navigation", "resource"].forEach((type) =>
  observer.observe({ type, buffered: true }),
);

This would log a JSON object like so:

json
{
  "name": "cache",
  "duration": 23.2,
  "description": "Cache Read"
}

To get a JSON string, you can use JSON.stringify(serverEntry) directly; it will call toJSON() automatically.

Specifications

Specification
Server Timing
# dom-performanceservertiming-tojson

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
toJSON

Legend

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Full support
Full support