Semantic conventions for browser events

Status: Development

This document defines semantic conventions for browser (web) instrumentations that emit events.

WebVital Event

Status:

The event name MUST be browser.web_vital.

This event describes the website performance metrics introduced by Google, See web vitals.

Attributes:

Key	Stability	Requirement Level	Value Type	Description	Example Values
browser.web_vital.delta		Required	double	The delta between the current value and the last-reported value. See delta.	0.2
browser.web_vital.id		Required	string	A unique ID representing this particular metric instance.	v3-1677874579383-6381583661209
browser.web_vital.name		Required	string	Name of the web vital.	cls
browser.web_vital.value		Required	double	Value of the web vital.	1.0
browser.web_vital.navigation_type		Recommended	string	The type of navigation, as reported by the Navigation Timing API, with additional values reported by the web-vitals library.	navigate
browser.web_vital.rating		Recommended	string	The rating of the web vital value against the “good”, “needs improvement”, and “poor” thresholds defined for the metric.	good

browser.web_vital.name has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
cls	Cumulative Layout Shift. See cls.
fcp	First Contentful Paint. See fcp.
inp	Interaction to Next Paint. See inp.
lcp	Largest Contentful Paint. See lcp.
ttfb	Time to First Byte. See ttfb.

browser.web_vital.navigation_type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
back-forward	Navigation through the browser’s history traversal (e.g. back/forward buttons).
back-forward-cache	Navigation restoring a page from the back/forward cache (bfcache).
navigate	Navigation started by clicking a link, entering a URL, form submission, or a script operation.
prerender	Navigation to a page that was prerendered.
reload	Navigation through a reload operation or a Location.reload() call.
restore	Navigation restoring a page that was previously discarded by the browser.

browser.web_vital.rating has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
good	The metric value is within the “good” threshold.
needs-improvement	The metric value is within the “needs improvement” threshold.
poor	The metric value is within the “poor” threshold.