PerformanceServerTiming

{{APIRef("Performance API")}} {{AvailableInWorkers}} {{securecontext_header}} 

The PerformanceServerTiming interface surfaces server metrics that are sent with the response in the {{HTTPHeader("Server-Timing")}}  HTTP header.

This interface is restricted to the same origin, but you can use the {{HTTPHeader("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.

Instance properties

• {{domxref('PerformanceServerTiming.description')}}  {{ReadOnlyInline}} 
  • : A string value of the server-specified metric description, or an empty string.
• {{domxref('PerformanceServerTiming.duration')}}  {{ReadOnlyInline}} 
  • : A double that contains the server-specified metric duration, or value 0.0.
• {{domxref('PerformanceServerTiming.name')}}  {{ReadOnlyInline}} 
  • : A string value of the server-specified metric name.

Instance methods

• {{domxref('PerformanceServerTiming.toJSON()')}} 
  • : Returns a JSON representation of the PerformanceServerTiming object.

Example

Given a server that sends the {{HTTPHeader("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 {{domxref("PerformanceResourceTiming.serverTiming")}}  property and live on navigation and resource entries.

Example using a {{domxref("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.

const observer = new PerformanceObserver((list) => {
  list.getEntries().forEach((entry) => {
    entry.serverTiming.forEach((serverEntry) => {
      console.log(
        `${serverEntry.name} (${serverEntry.description}) duration: ${serverEntry.duration}`,
      );
      // Logs "cache (Cache Read) duration: 23.2"
      // Logs "db () duration: 53"
      // Logs "app () duration: 47.2"
    });
  });
});

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

Example using {{domxref("Performance.getEntriesByType()")}} , which only shows navigation and resource performance entries present in the browser’s performance timeline at the time you call this method:

for (const entryType of ["navigation", "resource"]) {
  for (const { name: url, serverTiming } of performance.getEntriesByType(
    entryType,
  )) {
    if (serverTiming) {
      for (const { name, description, duration } of serverTiming) {
        console.log(`${name} (${description}) duration: ${duration}`);
        // Logs "cache (Cache Read) duration: 23.2"
        // Logs "db () duration: 53"
        // Logs "app () duration: 47.2"
      }
    }
  }
}

Specifications

{{Specifications}} 

Browser compatibility

{{Compat}} 

See also

• {{HTTPHeader("Server-Timing")}} 
• {{domxref("PerformanceResourceTiming.serverTiming")}}