Safari 26.2 adds support for measuring Largest Contentful Paint (LCP) and the Event Timing API, which is used to calculate Interaction to Next Paint (INP). This enables site owners to collect Largest Contentful Paint (LCP) and Interaction to Next Paint (INP) data from Safari users through the browser Performance API using their own analytics and real user monitoring tools.
LCP And INP In Apple Safari Browser
LCP is a Core Web Vital and a ranking signal. Interaction To Next Paint (INP), also a Core Web Vitals metric, measures how quickly your website responds to user interactions. Native Safari browser support enables accurate measurement, which closes a long-standing blind spot for performance diagnostics of site visitors using Apple devices.
INP is a particularly critical measurement because it reports on the total time between a user’s action (click, tap, or key press) and the visual update on the screen. It tracks the slowest interaction observed during a user’s visit. INP is important because it enables site owners to know if the page feels “frozen” or laggy for site visitors. Fast INP scores translate to a positive user experience for site visitors who are interacting with the website.
No Effect On CrUX, PageSpeed Insights, Or Search Console
This change will have no effect on public tools like PageSpeed Insights, Google Search Console, and CrUX data because they are Chrome-based.
However, Safari site visitors can now be included in field performance data where site owners have configured measurement, such as in Google Analytics or other performance monitoring platforms.
The following analytics packages can now be configured to surface these metrics from Safari browser site visitors:
- 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
Apple Safari’s update also enables Real User Monitoring (RUM) platforms to surface this data for site owners:
- Akamai mPulse
- Cloudflare Web Analytics
- Datadog RUM
- Dynatrace
- Elastic Observability (RUM)
- New Relic Browser
- Raygun
- Sentry Performance
- SpeedCurve
- Splunk RUM
Apple’s official documentation explains:
“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.”
Safari Will Not Support CLS
Cumulative Layout Shift (CLS) is a Core Web Vital metric that measures how stabile the web page is in terms of page elements moving around and shifting while the user is looking at the page. A poor CLS score indicates a bad user experience caused by a user trying to read or interact with page elements and missing because the page elements keep shifting around.
A Google’s Web.dev’s blog post about this topic shared that Safari will not support CLS reporting but it may arrive as a feature in 2026.
“The third Core Web Vital is Cumulative Layout Shift (CLS), and is not part of the Interop 2025 project—though it has been proposed for Interop 2026. For now, it is not supported beyond Chromium-based browsers.”
Small Differences Between Chrome And Safari Scores
Google’s Web.dev team posted that there are only slight differences between Chrome and Safari CWV scores, measurable in milliseconds, so the differences aren’t of any consequence.
They explained:
“The end of the rendering loop is broadly interoperable and is defined as the paintTime. However after this, there is a later presentationTime which is implementation-specific and aims to indicate when the pixels are actually drawn on the screen. Chrome measures LCP up until the end of presentationTime, while Firefox and Safari don’t include presentationTime and so measure until the earlier paintTime. This results in slight milliseconds of difference between the measures. From Chrome 145, the paintTime measure will also be exposed for LCP for those that want to be able to compare like for like across browsers.
The same difference applies to INP as well.”
Safari 26.2 provides new data that is critical for SEO and for monitoring the user experience, information that site owners rely on. Safari traffic represents a significant share of site visits. These improvements make it possible for site owners to have a more complete view of the real user experience across more devices and browsers.
