| # INP, LCP, and FCP Changes in Chrome 126 |
| |
| ## Launch NewPresentationFeedbackTimeStamps to 100% Stable on Mac |
| |
| The GPU [PresentationFeedback](https://source.chromium.org/chromium/chromium/src/+/main:ui/gfx/presentation_feedback.h) |
| parameters contain an estimated [timestamp](https://source.chromium.org/chromium/chromium/src/+/main:ui/gfx/presentation_feedback.h;l=57?q=%22base::TimeTicks%20timestamp;%22&ss=chromium%2Fchromium%2Fsrc) |
| for the time when the frame will be presented on a screen. |
| The old PresentationFeedback records the time when the CALayerTree of the |
| frame is populated to CoreAnimation instead of the actual time when the image |
| content of the CALayerTree is displayed on a screen. This feature improves the |
| metrics accuracy by using the image content display time for |
| PresentationFeedback. As a result, the time for producing a frame on a screen |
| increases. |
| |
| ## How does this affect a site's metrics? |
| |
| On average, the feature NewPresentationFeedbackTimeStamps increases the latency |
| of INP, LCP and FCP by ~20 ms. The actual numbers can change according to the |
| hardware screen VSync frame interval. |
| |
| ## When were users affected? |
| |
| This feature was launched to 100% Stable on Mac on June 17, 2024 for Chrome 124 |
| and beyond during the release period of Chrome 126. Chrome 126 was released the |
| week of June 11. |
| |
| Note: The [source code change](https://chromiumdash.appspot.com/commit/39dd592ae4ca58ea98263802a177c88c86f0d519) |
| for enabling this feature was merged into the M128 branch. |
| |
