Though the NoibuJS script can and does collect web vital information from sessions on Safari, the browser introduces some special cases that may impact how this data is collected and displayed. Furthermore, older versions of Safari may not support certain vitals. Review the notes below for a summary of these differences.
First Input Delay (FID)
Safari does not yet provide native support for the Event Timing API, which is the API that usually powers the FID metric. The web vitals library generally uses a polyfill or fallback to approximate this metric on unsupported browsers, including Safari.
Largest Contentful Paint (LCP)
Safari added support for the Largest Contentful Paint API starting in Safari 14. Therefore, this metric should work provided the shopper is using Safari 14 or above. For earlier versions, the metric may not be available.
Cumulative Layout Shift (CLS)
CLS is also generally supported in Safari 14 and above. Prior versions may not support the Layout Instability API, which is used to measure this metric.
Learn more about Web Vitals.