# Semantic conventions for browser events **Status**: [Development][DocumentStatus] 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](https://web.dev/vitals). **Body fields:** :warning: Body fields will be moved to complex attributes once the semantic convention tooling supports complex attributes (see [#1870](https://github.com/open-telemetry/semantic-conventions/issues/1870)). | Body Field | Type | Description | Examples | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability | |---|---|---|---|---|---| | `delta` | double | The delta between the current value and the last-reported value. See [delta](https://github.com/GoogleChrome/web-vitals?tab=readme-ov-file#report-only-the-delta-of-changes). | `0.2` | `Required` |  | | `id` | string | A unique ID representing this particular metric instance. | `v3-1677874579383-6381583661209` | `Required` |  | | `name` | enum | Name of the web vital. | `cls` | `Required` |  | | `value` | double | Value of the web vital. | `1.0` | `Required` |  | `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](https://web.dev/articles/cls). |  | | `fid` | First Input Delay. See [fid](https://web.dev/articles/fid). |  | | `inp` | Interation to Next Paint. See [inp](https://web.dev/articles/inp). |  | | `lcp` | Largest Contentful Paint. See [lcp](https://web.dev/articles/lcp). |  | [DocumentStatus]: https://opentelemetry.io/docs/specs/otel/document-status