Intent to Extend Experiment (again): User-Agent Reduction

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Mike Taylor

Oct 17, 2022, 3:36:34 PM10/17/22
to blink-dev

Hi there,

We would like to extend the User-Agent Reduction OT again, from M107 to M111 (inclusive). As announced in our I2S for “Phase 5”, we intend to roll out the next phase of UA reduction gradually until M111. We’ve received a request from the ecosystem that it would benefit testers and developers to continue testing with the user-agent reduction until the rollout to general availability reaches 100%, which seems very reasonable.

(We might come back and ask for another extension for “Phase 6” testing, but let’s wait until there’s demand for that.)

Original I2E 

First I2EE 

Second I2EE 

Experiment Timeline

M107-M111 inclusive

Reason this experiment is being extended

Like the previous extension, we believe the risks for burn-in don't apply, because this OT just enables what we are planning to ship as default behavior in the future (and the OT stopped working last week).

We still have not received negative feedback or reports of breaking from OT participants, and are encouraged by that fact.

Here’s the relevant info required for OT extensions beyond 6 milestones:

Draft spec: 

TAG review: requests

  • Gecko: Shipped/Shipping. Firefox has frozen (or capped) much of their UA string already.

  • WebKit: Shipped/Shipping. Safari has already frozen everything in their UA string except for version number info.

  • Web developers: Mixed signals. Reactions have ranged from positive to indifferent to negative, from various channels.

WPT tests

  • None yet, since UAs have flexibility to diverge here. With more alignment, this may make sense in the future.



Rick Byers

Oct 17, 2022, 4:50:15 PM10/17/22
to Mike Taylor, blink-dev
LGTM - agreed that there's little to no downside to a long-running trial here since this isn't about new functionality.

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