design-reviews#1285: Incubation: Declarative Performance Observer

#1285: Incubation: Declarative Performance Observer

Opened

Sep 28, 2026

GitHub repo: https://github.com/explainers-by-googlers/declarative-performance-observer
Primary contacts:
- Shunya Shishido (@sisidovski), Google, Proposer / Implementer
Organization/project driving the design: Google
This work is being funded by: Google
Incubation and standards groups that have discussed the design:
- WICG: https://github.com/WICG/proposals/issues/280
- Web Performance Working Group: Presented and discussed on June 18, 2026 (Minutes: https://w3c.github.io/web-performance/meetings/2026/2026-06-18/index.html)
Standards group(s) that you expect to discuss and/or adopt this work when it's ready: W3C Web Performance Working Group

Multi-stakeholder feedback:
- Chromium comments: Positive (proposer). The Chrome Loading team is actively implementing and experimenting with this feature in chromium (Origin Trial in M151–M155, tracking bug: https://crbug.com/505208781, ChromeStatus: https://chromestatus.com/feature/6594955352080384).
- Mozilla comments: https://github.com/mozilla/standards-positions/issues/1458
- WebKit comments: https://github.com/WebKit/standards-positions/issues/725
Major unresolved issues with or opposition to this design:
- No formal opposition has been expressed.
- Active design discussions on GitHub include:
  - Custom metadata / dimensions (Issue #8): Exploring how developers can safely attach custom application dimensions.
  - Long-lived SPA documents (Issue #7): How to best support same-document transitions / Soft Navigations alongside terminal lifecycle report emission.

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