PerformanceServerTiming

The PerformanceServerTiming interface surfaces server metrics that are sent with the response in the Server-Timing HTTP header.

This interface is restricted to the same origin, but you can use the Timing-Allow-Origin header to specify the domains that are allowed to access the server metrics. Note that this interface is only available in secure contexts (HTTPS) in some browsers.

PerformanceServerTiming.descriptionRead only

A DOMString value of the server-specified metric description, or an empty string.

PerformanceServerTiming.durationRead only

A double that contains the server-specified metric duration, or value 0.0.

PerformanceServerTiming.nameRead only

A DOMString value of the server-specified metric name.

PerformanceServerTiming.toJSON()

Returns a DOMString that is the JSON representation of the PerformanceServerTiming object.

Given a server that sends the Server-Timing header, for example a node.js server like this:

const http = require('http');

function requestHandler(request, response) {
  const headers = {
    'Server-Timing': `
      cache;desc="Cache Read";dur=23.2,
      db;dur=53,
      app;dur=47.2
    `.replace(/\n/g, '')
  };
  response.writeHead(200, headers);
  response.write('');
  return setTimeout(_ => {
   response.end();
 }, 1000)
};

http.createServer(requestHandler).listen(3000).on('error', console.error);

The PerformanceServerTiming entries are now observable from JavaScript via the PerformanceResourceTiming.serverTiming property:

let entries = performance.getEntriesByType('resource');
console.log(entries[0].serverTiming);
// 0: PerformanceServerTiming {name: "cache", duration: 23.2, description: "Cache Read"}
// 1: PerformanceServerTiming {name: "db", duration: 53, description: ""}
// 2: PerformanceServerTiming {name: "app", duration: 47.2, description: ""}

• Server-Timing
• PerformanceResourceTiming.serverTiming