Attendees
- Cliff Crocker
- Michal Mocny
- Nic Jansma
- Sergey Chernyshev
- Karlijn Lowik
- Erwin Hofman
- Ivailo Hristov
- Andy Davies
- Simeon Totev
- Dan Freeman
- Edwin Molina H.
- Gilberto Cocchi
- Yoav Weiss
- Eric Goldstein
- Philip Tellis
- Nev Wylie
Agenda
- Header adoption (Timing-Allow-Origin, Server-Timing)
Admin
- Next meeting: June 20 2025
AI Notes
Notes
Meeting Logistics & Updates (00:00 - 09:34)
- Meeting now using Fireflies AI for transcription instead of manual scribing
- Updates made to tracking project to monitor browser support for RUM features
- Ideas for creating a 'RUM feature baseline matrix' similar to Google's Baseline project
- Next meeting scheduled for June 20th (third Friday) due to holidays
- Simon offered to help with the baseline matrix development
Server Timing Header Discussion (09:34 - 25:56)
- Server Timing allows servers to communicate metrics to user agents through JavaScript
- Specification released around 2018, initially championed by Akamai
- Common CDN use cases include tracking cache hits, latency metrics, and origin vs. edge time
- Current adoption shows only ~6% of hosts implement server timing headers
- Multiple naming conventions across CDNs create challenges for consistent tracking
- Akamai, Cloudflare, Cloudfront, and Shopify mentioned as implementers
- Server timing usage in JavaScript has increased from 12% to 34% in the past year
Resource Timing & TAO Adoption (25:56 - 35:31)
- Only 25% of third-party requests use Timing Allow Origin headers
- Research showed only ~27% of resources are 'fully visible' to RUM providers due to TAO limitations
- 53% of resources have restricted visibility (can see URL but not detailed metrics)
- 18% of resources completely invisible to RUM due to cross-origin iframe restrictions
- These limitations impact ability to accurately measure total page weight and resource timing
- Over 70% of sites using TAO headers have it set to '*' (allowing all origins)
Use Cases & Implementation Discussion (35:31 - 51:48)
- Shopify uses server timing on subresources to measure processing duration
- Yoav asked about interest in server timing trailers (supported by Firefox but not Chrome)
- Sergey highlighted different use cases for server timing on main HTML vs. resources
- Etsy used server timing for cache status on CDN resources, especially for images
- Akamai adds server timing to all resources including HTML, exposing edge time, origin time and cache data
- Discussion about standardization challenges due to different implementation details across providers
️ Strategies for Improving Adoption (51:48 - 01:00:32)
- Group proposed creating best practices documents from the RUMCG
- Idea to maintain a registry of server timing implementations and their meanings
- Suggestion to provide 'recipes' for implementing server timing on different platforms
- Discussion of HTML spec proposal (#8143) for a 'public resource' header that could simplify TAO adoption
- Karlijn suggested increased publicity of success stories to drive competitive adoption
- Plan to file GitHub issues to track these suggestions and solicit community participation
- Brief update on previous discussions about potential external funding for projects
Action items
Nic Jansma
- File GitHub issues in RUMCG repository for the discussed ideas around Server Timing and TAO header adoption (54:56)
- Share issue links in the Slack channel for community input (57:00)
- Link the deck about cache status proposal in the meeting notes (53:42)
Simon Totev
- Connect with chairs via Slack channel to help with the RUM feature baseline matrix development (09:34)
All Participants
- Provide feedback on using Fireflies AI for meeting transcription (07:14)
- Comment on the HTML issue #8143 regarding 'public resource' header proposal to show support (52:42)