---
agentTools:
  projectIndex: https://support.speedcurve.com/llms.txt
---

# RUM update: lux.js v308

**24 May 2023 (UTC)**

### New features

* Pages that are [prerendered](https://web.dev/speculative-prerendering/) are now flagged as such.
* Pages that are restored from the [back-forward cache (bfcache)](https://web.dev/bfcache/) can now be tracked by setting `LUX.newBeaconOnPageShow = true`. [Read the documentation](https://support.speedcurve.com/docs/rum-js-api#luxnewbeacononpageshow) for more information on how this works.
* Server timing metrics are now extracted from the main page response. Metrics must be configured in your SpeedCurve settings before they are collected.

### Improvements

* The beacon will no longer be sent automatically if the page visibility is hidden. This can be overridden by setting `LUX.trackHiddenPages = true`.
* All metrics on prerendered pages are now relative to `activationStart`.
* Navigation timing values with a value of zero are now reported, rather than ignored.
* The legacy `domLoading` metric is no longer collected.
* The first paint event of any type will be considered for start render, rather than just first-paint events.

### Bug fixes

* Timing values are now rounded down to the nearest unit to prevent values from being rounded into the future.