Server-Timing

The Server-Timing header communicates one or more metrics and descriptions for a given request-response cycle. It is used to surface any backend server timing metrics (e.g. database read/write, CPU time, file system access, etc.) in the developer tools in the user's browser or in the PerformanceServerTiming interface.

Header type Response header
Forbidden header name no

Syntax

The syntax of the Server-Timing header allows you to communicate metrics in different ways: server metric name only, metric with value, metric with value and description, and metric with description.

The specification advices that names and descriptions should be kept as short as possible (use abbreviations and omit optional values where possible) to minimize the HTTP overhead.

// Single metric without value
Server-Timing: missedCache

// Single metric with value
Server-Timing: cpu;dur=2.4

// Single metric with description and value
Server-Timing: cache;desc="Cache Read";dur=23.2

// Two metrics with value
Server-Timing: db;dur=53, app;dur=47.2

// Server-Timing as trailer
Trailer: Server-Timing
--- response body ---
Server-Timing: total;dur=123.4

Privacy and security

The Server-Timing header may expose potentially sensitive application and infrastructure information. Consider to control which metrics are returned when and to whom on the server side. For example, you could only show metrics to authenticated users and nothing to the public.

PerformanceServerTiming interface

In addition to having Server-Timing header metrics appear in the developer tools of the browser, the PerformanceServerTiming interface enables tools to automatically collect and process metrics from JavaScript. 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. The interface is only available in secure contexts (HTTPS) in some browsers.

Specifications

Specification Status Title
Server Timing
The definition of 'Server-Timing Header Field' in that specification.
Working Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 65Edge ? Firefox Full support 61IE No support NoOpera Full support 52Safari ? WebView Android Full support 65Chrome Android Full support 65Edge Mobile ? Firefox Android Full support 61Opera Android Full support 52Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Contributors to this page: kronthto, cvazac, fscholz
Last updated by: kronthto,