Apple Safari Update: Core Web Vitals LCP & INP Tracking

Apple's latest Safari update, version 26.2, marks a significant advancement for web performance and SEO, enabling site owners to accurately measure two crucial Core Web Vitals metrics: Largest Contentful Paint (LCP) and Interaction to Next Paint (INP). This enhancement closes a critical data gap, providing unprecedented insights into the user experience for Safari users and ensuring a more complete picture of website performance across all major browsers.

Understanding LCP and INP in Safari

Safari 26.2 now supports the measurement of Largest Contentful Paint (LCP) and the Event Timing API, which is essential for calculating Interaction to Next Paint (INP). These are not just technical metrics; they are fundamental to how users perceive a website's speed and responsiveness. LCP, a key Core Web Vital and a Google ranking signal, measures how quickly the largest visible content element on a page loads. A fast LCP score indicates that a page feels loaded quickly to the user.

INP, also a Core Web Vital, assesses how swiftly your website responds to user interactions like clicks, taps, or key presses. It tracks the slowest interaction during a user's visit, reporting the total time from action to visual update on the screen. A high INP score can signal that a page feels "frozen" or laggy, directly impacting user satisfaction. Native Safari browser support for these metrics means site owners can now accurately diagnose and improve performance for a significant segment of their audience – those using Apple devices.

Impact on Performance Monitoring and Analytics

While public tools like PageSpeed Insights and CrUX data, which are Chrome-based, will not be directly affected by this Safari update, the change is transformative for site owners utilizing their own analytics and real user monitoring (RUM) tools. This update allows for the collection of LCP and INP data from Safari users via the browser's Performance API, integrating Apple device user data into field performance reports.

Site owners can now configure various analytics packages to surface these critical metrics from Safari browser visitors, including:

• Google Analytics (GA4, via Web Vitals or custom event collection)
• Adobe Analytics
• Matomo
• Amplitude (with performance instrumentation)
• Mixpanel (with custom event pipelines)
• Custom / In-House Monitoring

Furthermore, leading Real User Monitoring (RUM) platforms are now equipped to provide this valuable data:

• Akamai mPulse
• Cloudflare Web Analytics
• Datadog RUM
• Dynatrace
• Elastic Observability (RUM)
• New Relic Browser
• Raygun
• Sentry Performance
• SpeedCurve
• Splunk RUM

Official Explanation from Apple's WebKit

Apple's official documentation on the WebKit blog elaborates on these new capabilities:

“Safari 26.2 adds support for two tools that measure the performance of web applications, Event Timing API and Largest Contentful Paint.

The Event Timing API lets you measure how long it takes for your site to respond to user interactions. When someone clicks a button, types in a field, or taps on a link, the API tracks the full timeline — from the initial input through your event handlers and any DOM updates, all the way to when the browser paints the result on screen. This gives you insight into whether your site feels responsive or sluggish to users. The API reports performance entries for interactions that take longer than a certain threshold, so you can identify which specific events are causing delays. It makes measuring “Interaction to Next Paint” (INP) possible.

Largest Contentful Paint (LCP) measures how long it takes for the largest visible element to appear in the viewport during page load. This is typically your main image, a hero section, or a large block of text — whatever dominates the initial view. LCP gives you a clear signal about when your page feels loaded to users, even if other resources are still downloading in the background.”

The integration of LCP and INP measurement in Safari 26.2 provides site owners with crucial data for both SEO and enhancing the overall user experience. Given that Safari traffic accounts for a significant portion of web visits, these improvements are vital. They empower website administrators with a more complete and accurate understanding of real user performance across a wider array of devices and browsers, enabling more informed optimization strategies.