PerformanceServerTiming: description property

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 description read-only property returns a string value of the server-specified metric description, or an empty string.

Value

A string.

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(
        `${serverEntry.name} (${serverEntry.description}) duration: ${serverEntry.duration}`,
      );
      // Logs "cache (Cache Read) duration: 23.2"
    });
  });
});

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

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

js
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"
      }
    }
  }
}

Specifications

Specification
Server Timing
# dom-performanceservertiming-description

Browser compatibility

BCD tables only load in the browser

See also