Dec 12, 2025 | RUMCG Meeting

Attendees

• Cliff Crocker
• Nic Jansma
• Karlijn Lowik
• Barry Pollard
• Erwin Hofman
• Mateusz Krzeszowiak
• Michal Mocny
• Sergey Chernyshev
• Yoav Weiss
• Ivalio Hristov
• Martin Alderson
• Gilberto Cocchi

Agenda

• 2025 Recap
• RUM RUM
• TPAC 2025
• 2026 Agenda

Admin

• Skipping January 2026
• Next meeting: February 2026

AI Notes

Summary

• Meeting Schedule Change: Regular meetings move to Wednesdays at 10am Eastern, starting February 11th, 2026. January meeting skipped.
• Focus Shift: The group aims to advance header adoption and server timing, pushing for actionable outcomes instead of just discussions.
• Event Recap: RUM RUM meetup had 80 attendees; next year’s event in Google office planned due to growing interest and engagement.
• TPAC Updates: Chrome is rolling out speculation rules; Soft Navigation API updates will affect interaction reporting and usability.
• Metric Challenges: Need for clear best practices on metrics like INP; group discusses potential higher-level abstractions to improve metric adoption.
• Future Topics: Emerging proposals like CPU performance API and navigation confidence API highlighted for future monitoring and discussions in 2026.

Meeting Scheduling and Cadence

The group decided to shift the regular meeting day from Friday to Wednesday at 10am Eastern, starting with the next meeting on February 11th, 2026 to improve attendance and reduce conflicts (06:04).

• The January meeting will be skipped due to widespread holiday schedules and low expected attendance.
• Wednesday was preferred by most participants, including key members like Barry Pollard, despite initial concerns about timing.
• This change aims to maintain regular engagement while accommodating vacation and workload patterns.
• The chairs will monitor attendance and can revert the schedule if needed.

Community Group Recap and Forward Planning

The group reflected on the past year’s progress and emphasized the need to move from discussion to concrete advances on key topics like header adoption and server timing (08:37).

• Nic Jansma highlighted the desire to adopt and advance one or two issues in the coming months rather than just discussing them.
• Karlijn Lowik proposed focusing on header adoption with the goal of creating clear guidelines or a statement to drive broader implementation.
• The group plans to revisit updates on Interop and Core Web Vitals in February, especially with 2026 spec decisions expected in February (10:58).
• Barry Pollard recommended scheduling a follow-up agenda item in September to support proposals with developer demand and platform backing, citing Shopify’s interest as an example.

RUM CG and TPAC Event Insights

The RUM RUM meetup in Amsterdam and the TPAC conference in Kobe were praised for fostering collaboration and sharing progress across browser vendors and industry players (18:59).

• Cliff Crocker and Barry Pollard commended organizers Caroline Lowik and Barry for successful coordination and engagement.
• The RUM RUM event drew approximately 80 attendees, including new participants from DataDog and Catchpoint, proving the group’s growing influence (21:08).
• The group plans to repeat the event next year and has already taken steps to book the Google office space for it (27:27).
• Discussions at RUM RUM raised significant interest in AI browsers and CDN roles in web performance, suggesting future focused sessions on those topics (22:26).
• A vendor-agnostic survey of the performance ecosystem was proposed to better understand investments and innovation across browsers, CDNs, and measurement tools.

TPAC Technical Updates and Standards Discussion

The TPAC sessions covered key updates on features relevant to real user monitoring, such as speculation rules, soft navigation, and scroll performance, with active cross-browser interest and ongoing origin trials (30:45).

• Barry Pollard reported that speculation rules are rolling out in Chrome, with Safari’s implementation under review and Mozilla showing early interest, indicating growing cross-browser alignment (30:45).
• Michal Mocny detailed planned updates to the Soft Navigation API, including changing how interaction paints are reported before navigation and handling URL replaceState differently, aiming for improved accuracy and usability (35:56).
• The current Soft Navigation origin trial will end with Chrome 144 in late January, with potential extension discussed to allow more feedback and smooth rollout, pending decisions by end of Q1 2026 (39:18).
• Improvements to scroll event measurement were highlighted, with Microsoft proposing new events to better track scroll smoothness and end times, which could benefit RUM use cases (32:33).

Metrics Specification and Implementation Challenges

The group discussed the complexities around defining and implementing derived metrics like INP (Interaction to Next Paint) and the need for clear best practice documentation beyond raw specs (45:08).

• There was consensus that the Web Performance Working Group should include a non-normative section in the event timing spec to clarify INP’s definition and usage, helping standardize implementations (45:13).
• Barry Pollard emphasized challenges in maintaining the metric’s reference implementation and ownership, noting that current documentation is fragmented between blogs, specs, and libraries.
• Sergey Chernyshev and Mateusz Krzeszowiak stressed that consistent best practices are essential to build trust and avoid inconsistent metric collection that could confuse developers and product managers (50:40).
• The group considered whether browsers should provide higher-level abstractions for complex metrics to reduce errors and ease adoption, reflecting on the heavy reliance on the Web Vitals JS library.
• Cliff Crocker compared this to the success of the server timing specification’s best practice approach and suggested the community group could own a simple, authoritative guidance document.
• The discussion recognized that practical deployment nuances, like filtering outliers and handling visibility changes, are as important as metric definitions.

Emerging Proposals and Future Topics

Several new proposals and initiatives with potential impact on RUM were flagged for monitoring and future discussion (55:21).

• A CPU performance API proposal aims to bucket devices by performance capability to help sites tailor experiences; although still in early stages, shipping behind flags is anticipated soon (55:21).
• The group plans to revisit this in February, with Barry Pollard offering to provide updates once shipping details are clearer.
• The navigation confidence API from Microsoft, currently in Origin Trial, offers a privacy-preserving way to classify navigations; it may ship in Chrome 145 and is relevant for bias correction in metrics (57:44).
• These emerging APIs align with the group’s interest in improving measurement fidelity and handling bot or AI-driven traffic appropriately.
• The backlog includes topics like bot and bad actor detection and AI browser identification, which are expected to become major discussion points in 2026.

Closing and Community Engagement

The meeting concluded with thanks and holiday wishes, reinforcing the group’s positive momentum after a successful first year (59:31).

• Chairs encouraged ongoing Slack discussions for agenda planning and welcomed feedback on topics.
• Members were reminded of the value of the RUM CG for sharing knowledge and influencing web performance standards and practices.
• The next meeting is set for mid-February, marking the start of a new cycle focused on advancing standards and practical improvements.

Action items

Nic Jansma

• Reschedule next RUMCG meeting to Wednesday February 11, 2026 and update calendar invites accordingly (06:45)
• Share and facilitate discussion on backlog and key 2026 topics including header adoption, core web vitals interop, and soft navigation feedback (16:35)
• Continue engaging on INP metric definition and coordination with Web Performance Working Group to incorporate a non-normative spec note (44:45)

Michal Mocny

• Share list of collected feedback on Soft Navigation origin trial and expected changes, including interaction contentful paint updates (36:10)
• Collect further participant feedback on origin trial usage and communicate plans for potential extension or final deployment (43:45)

Barry Pollard

• Track and provide updates on CPU performance API shipping status and coordinate presenting “berry baits” update at upcoming meetings (57:10)
• Follow up on navigation confidence API progress and browser interest for RUMCG monitoring (58:00)
• Compile agenda item(s) for the RUMCG summarizing core vital metrics implementations and better developer guidance for February meeting (11:40)

Karlijn Lowik

• Coordinate with Barry and others to organize next RUMCG session logistics and possible vendor demos or presentations on CDN performance and AI browser topics (23:15)

Erwin Hofman

• Provide input and feedback regarding soft navigations origin trial expansion and share insights from client usage on soft labs (38:00)

Group-wide

• Review latest TPAC meeting minutes, recordings, and Web Performance Working Group materials to stay informed about speculation rules, scroll performance, and soft navigation developments (29:20)
• Provide feedback to Michal on soft navigation origin trial participation and testing results as soon as practical (43:40)
• Continue conversations in Slack or email threads on topics such as AI browsers, bot detection, and core vital interoperability ahead of February meeting (59:10)