Soft Navigation Heuristics Changelog

This is a list of changes to Soft Navigation Heuristics.

• Chrome 148

  • Metric bug fix: Use correct NavigationId for InteractionContentfulPaint entries (59bc92edc430c).

• Chrome 147 (Major changes after origin trial expired & preparing to extend OT for 3 milestones)

  • InteractionContentfulPaint decoupled from SoftNavigationEntry and reported for all interactions.
    • InteractionContentfulPaint entries now emit as soon as they occur, for any interaction, rather than waiting for a Soft Navigation to become detected first (e8815d0acaf2f).
    • The same semantics used to measure soft-navigation loading performance can be used to measure any dynamic content updates, even when the URL doesn't change.
  • SoftNavigationEntry adds largestInteractionContentfulPaint attribute.
    • SoftNavigationEntry entries now report a largestInteractionContentfulPaint attribute. Because InteractionContentfulPaint entries are now decoupled from soft-navigations, this makes it more convenient to track soft-LCP for soft navs, specifically.
  • Aligned "Interaction Detection" with INP.
    • Changed the implementation to reuse the existing Event Timing API mechanism for detecting interactions.
    • To accomplish this, added support for measuring Event Timing for navigate, popstate, and hashchange events (c6a49e314dfb5), however, these Event Timing entry types are not yet exposed to the performance timeline.
    • Added interactionId attribute to InteractionContentfulPaint and SoftNavigationEntry performance entries (704c0222f53a3).
  • Added support for replaceState.
    • Added support for triggering soft navigations on replaceState (in addition to pushState).
    • Exposed the navigationType (279eb27b6d2bb).
  • Refined TimeOrigin (to measure more time).
    • Previously, TimeOrigin was a complicated value, something akin to min(processingEnd, urlChangeTime) and was meant to match hard-navs cross-document navigationStart, but this model proved confusing and undesired.
    • Changed InteractionContentfulPaint and SoftNavigationEntry to report startTime equal to Interaction startTime (12b7e08417957).
  • Other implementation changes:
    • Set up paint tracking for inline style and class attribute changes (50dc1d52a77ca).
    • Improved browser-side soft navigations tracking (a431cb877c128).

• Chrome 140 - 144 (Addressing bugs during origin trial)

  • Metric bug fix: Refactor pending InteractionContentfulPaint entry buffering (abe0507666c40).
  • Metric bug fix: Ensured correct navigation ID is used for entries from SoftNavigationContext (5bdc6551839e7).
  • Metric bug fix: Improve recording soft navigations in UKM (correct URL) (5c510d4ea6310).
  • Metric bug fix: Fixed browser-initiated intercepted back navigations (b0c3c8bac14d0).

• Chrome 139 (Major revamp completed & new origin trial started)

  • Major revamp of Soft Navigation Heuristics.
    • This release included a large overhaul of the detection mechanics to improve accuracy and performance.
    • This work culminated in Chrome 139, and we started a new 6 milestone origin trial: https://developer.chrome.com/blog/new-soft-navigations-origin-trial.
  • Each Interaction now has independent painted area tracking.
    • Moved painted area tracking into each Context (a2a9986393624) and removed the global "Initial area" requirement (7321c9f17fd69).
    • Explicitly supported dynamic content updates (in PaintTimingDetectors), rather than the need to "reset LCP" (e6d3c7c1267d7).
  • Introduced InteractionContentfulPaint PerformanceEntry.
    • Added the InteractionContentfulPaint entry to observe paint timings directly tied to interactions (88847f08dc064). This replaces "soft" LCP entries and removes the need for includeSoftNavigationObservations flag.
    • Each interaction will stop soft-LCP attribution at the first discrete input or scroll (cbb9d4e7c5eb3).
  • Integrated PaintTimingMixin into SoftNavigationEntry for FCP.
    • See (7ef307610e5e9).
  • Expanded DOM modification triggers.
    • Add <video> and image src changes as DOM modifications (82614425d92f0, 11dd080af48a9).
  • Other implementation changes:
    • Introduced advanced paint attribution modes (Pre-Paint based and lazy bottom-up tree walk) (7dacb1ba603ea, 9f42b77c0cb66).
    • Changed NavigationID to report a number instead of a UUID (c701061e45c73).
    • Replaced NodeFlags::kModifiedBySoftNavigation bit (which would persist forever) with per-context maps (4a275bc93d519).
    • Improved support for multiple URL changes within a context (eb71cbb21b410).
    • Optimized ModifiedDOM calls and context validation checks (fe01d34922570, 1e8e9dc69d467).

• Chrome 122

  • The 2% paint threshold now must be reached by each new soft navigation.
  • The start time of the soft navigation entry now marks the processing end time of the user interaction which triggered it.
  • Elements painted after an interaction, but before a soft navigation is detected will only count as LCP candidates if their paints are attributable to the interaction.

• Chrome 121

  • The paint threshold is reduced from 20% to 2%.

• Chrome 120

  • The first soft navigation on a page now also requires, in addition to the URL and DOM change, that the user interaction triggers a threshold amount of painting on the page.
  • This threshold is set to 20% of the amount which was painted before the page's very first user interaction. (Subsequent navigations do not require this, due to a bug)

• Chrome 119

  • Keyboard events can now trigger soft navigations.

• Chrome 117

  • FP and FCP entries are no longer emitted after soft navigation (without a command-line flag).

• Chrome 115

  • Navigation ID is changed to a random UUID in performance entries.

• Chrome 112

  • Performance observers need to be created with a flag to see FP, FCP and LCP events after soft navigation.

• Chrome 110: Initial origin trial release of soft navigation heuristics.

  • Soft navigation requires a click event to trigger both a URL change and an addition to the DOM, in any order.
  • Soft navigation entries are exposed to performance observers, as well as FP, FCP and LCP after each soft navigation.
  • Navigation id is included, and is a simple incrementing integer.